JP2006272058A - Centrifugal separator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce a moisture content of a discharge cake by enhancing the flow of a liquid staying in a precipitation layer in a discharge port direction in a decanter type centrifugal separator. <P>SOLUTION: The centrifugal separator is provided with a cylindrical bowl 1; and a screw conveyor 10 rotating coaxially to the bowl 1 in the same direction with a rotation speed difference in the bowl 1. The precipitation layer (b<SB>1</SB>) is separated from a treatment liquid (a) fed into the bowl 1 by centrifugal force, the discharge cake (b<SB>3</SB>) is discharged from a discharge port 7 provided near a bowl inner peripheral wall at one side of the bowl 1 and a separation liquid (c) is discharged from a discharge port 8 at the other side of the bowl 1. Projections 23 and 24 are provided on an outer peripheral surface of a rotation body 11 of the screw conveyor 10 and a helical impeller 12. A void is formed in the precipitation layer (b<SB>2</SB>) and easily makes the liquid staying in the precipitation layer (b<SB>2</SB>) flow in an axial and discharge port 8 direction. Since the separation liquid (c) staying in the precipitation layer (b<SB>2</SB>) is mixed into the discharge cake (b<SB>3</SB>) and is discharged, the water content is not reduced. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  TECHNICAL FIELD The present invention relates to a centrifugal separator that collects concentrated sewage sludge, industrial waste water, and various products for chemical and food industry, dewatering, precipitation heavy components, and recovered water by centrifugal force.

  Conventionally, a decanter type centrifugal separator is generally used for solid-liquid separation for separating a treatment liquid such as sludge into a solid and a liquid. In this type of decanter type centrifugal separator, the upper overflow method, the so-called negative device, is basically the position where the discharge port of the separated sediment layer (dehydrated cake) is equal to or higher than the liquid level in the bowl. It is in. Even if the head pressure in the bowl is used for discharge, the head pressure of the treatment liquid in the bowl is smaller than the head pressure of the heavy sediment layer, so it is impossible in principle to discharge only with the head pressure. Some sort of discharge mechanism is required. Here, a certain layer in the bowl is subjected to a strong pressing force due to the centrifugal force acting on the liquid layer or the sediment layer above it, which is the water head pressure. Further, in this specification, the direction in which the centrifugal force acts, that is, the direction far from the rotation axis of the bowl is referred to as “down” and the direction close to it is referred to as “up”.

  In Patent Document 1, in a decanter-type centrifuge, a centrifugal separator is used to discharge a dehydrated cake directly from a portion having the lowest moisture content in a bowl, thereby reducing moisture content and improving separation efficiency. A device is presented. As shown in FIG. 4, this apparatus is a centrifugal separator in which a screw conveyor 10 that rotates with a relative speed difference is housed in a bowl 1 that is rotated at a high speed, and a dewatered cake discharge path on the front end wall 2 of the bowl 1. 20, the opening 20a of the discharge path 20 into the bowl 1 is provided in the vicinity of the inner peripheral wall of the bowl, and the discharge port 20b to the outside of the end wall of the discharge path 20 is located at a higher position, that is, the radius of the inner peripheral wall of the bowl Smaller radius position.

In the above apparatus, the treatment liquid a to be dehydrated enters the supply chamber 14 from the supply pipe 16 as indicated by the arrow, and is supplied from the supply port 15 into the annular space 17, and the centrifugal force of the rotation of the bowl 1 and the screw conveyor 10. And is separated toward the front end in the bowl 1 by the spiral blade 12 fixed to the outer periphery of the rotary drum 11 of the screw conveyor 10. The separated liquid c, which is the separated liquid, is discharged out of the apparatus from the discharge port 8 on the rear end wall. On the other hand, the sediment layer b ₁ is scraped toward the front end of the bowl 1 by the spiral blade 12 and further subjected to separation action by centrifugal force, so that the separation of the remaining liquid proceeds and is consolidated to decrease the water content. precipitate layer b _2, and the the separated liquid c is also discharged from the discharge port 8.

Further, the sediment layer b ₂ conveyed to the front portion of the bowl 1 is accumulated at the front end of the annular space 17 by a difference from the discharge amount from the discharge path 20. This sedimentary layer has a specific gravity of about 2.5 to 3 if the sedimented heavy component is, for example, sand, and is much heavier than 1 of water. It becomes more than twice as compared with water. Furthermore, if the liquid level determined by the separated liquid discharge port 8 is lower than the rotary drum 11 of the screw conveyor 10 and a space remains between them, the deposited layer rises beyond the liquid level, and its specific gravity Depending on the size and the height of the rise, a large centrifugal head pressure acts in the vicinity of the opening 20a of the discharge path to produce a large consolidation effect on the sedimentary layer, and this centrifugal head pressure and the conveying force of the screw cause an extrusion action to the discharge path. Occurs.

As a result, the discharge cake b ₃ from the discharge path 20 is discharged only from the portion of the sediment layer b ₂ deposited on one end of the bowl 1 that has the highest consolidation effect due to the hydraulic head pressure of the centrifugal force acting on the deposit. It is discharged out of the bowl through which the centrifugal force is not applied via the path 20. As a result, of the sediment layer of the sediment in the bowl 1, only the hard part having the highest compaction effect, that is, the hard part having the lowest moisture content is directly discharged. the water content of the dehydrated cake b ₃ can be drastically reduced.
JP 2001-219097 A

However, in the conventional centrifugal separator, a phenomenon in which the water content of the discharged cake b ₃ is higher than the set value was observed. Moreover, when the rotation speed of the bowl 1 was increased, a phenomenon in which the decrease in the moisture content reached a peak was observed. The cause of this phenomenon is that the sediment layer b ₁ is scraped toward the front end of the bowl 1 by the spiral blade 12 and further separated by the centrifugal force, and the separation of the remaining liquid proceeds and is consolidated. decrease in water content Te precipitate layer b _2, and the when the separated liquid c is discharged from the discharge port 8, because the portion of the residual liquid fraction is discharged mixed in the discharge cake b _3. Thus the residual liquid fraction will be mixed in the exhaust cake b ₃ is precipitated layer b ₂ which is compacted has a low permeability for water, residual liquid content of the rotating cylinder 11 the middle precipitate layer b ₂ Since it takes time to move in the axial direction by permeation, it is considered that the movement ends and is discharged from the cake discharge port 7 together with the sediment layer b ₂ before flowing in the direction of the separation liquid discharge port 8. It is done.

  The present invention has been made in view of such problems, and an object thereof is to promote the flow of residual liquid in the sedimentation layer in the direction of the discharge port in the decanter type centrifugal separator, and to discharge it. It is to reduce the moisture content of the cake.

The invention according to claim 1 includes a cylindrical bowl that rotates in one direction, and a screw conveyor that rotates coaxially within the bowl and rotates in the same direction with a rotational speed difference. The heavy components are separated from the processing solution supplied into the inside of the bowl by centrifugal force, conveyed to one side of the bowl by the screw conveyor and accumulated, and pushed out from the heavy component discharge port provided on the one side. In the centrifugal separator provided on the other side of the bowl and discharged from the separation liquid discharge port, the surface of the one side or the other side of the spiral blade of the screw conveyor, or the rotary drum of the screw conveyor The centrifugal separator is characterized in that a protrusion is provided on an outer peripheral surface, and the liquid staying in the heavy component escapes in the direction of the separation liquid discharge port.
A second aspect of the present invention is the centrifugal separator according to the first aspect, wherein the protrusions are arranged in a spiral shape. Here, the spiral arrangement includes a case where the arrangement range is shorter than one rotation of the spiral. In addition, the spiral includes not only one whose turning radius is constant but also one that changes.

(Function)
According to the invention according to claim 1, by providing protrusions on the surface of the other side of the spiral blade of the screw conveyor or on the outer peripheral surface of the rotary drum of the screw conveyor, the heavy component is stirred, By releasing the staying liquid and forming a void through which the liquid flows, the liquid is guided in the axial direction toward the separated liquid discharge port.
According to the second aspect of the present invention, since the protrusions are arranged in a spiral shape, the voids in the heavy component are connected, so that the liquid staying in the heavy component is efficiently guided toward the discharge port.

  According to the present invention, in the decanter-type centrifuge, the moisture content of the discharged cake can be reduced by promoting the flow of the liquid remaining in the heavy component in the direction of the discharge port.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a longitudinal sectional view in the axial direction of a centrifugal separator according to an embodiment of the present invention, and FIG. 2 is a perspective view of the screw conveyor. In these drawings, the same components as those in FIG. 4 are denoted by the same reference numerals.

  As shown in FIG. 1, in this centrifugal separator, a bowl (outer rotating cylinder) 1 has a straight cylindrical shape that is a horizontal cylinder, and is hollow at the center of the drainage chamber wall 6 and the rear end wall 3 at its front end. The shafts 4 and 5 are protruded, are rotatably supported by a bearing (not shown), and are rotated at high speed by a driving device. A plurality of mud discharge ports 7 are provided at regular intervals along the circumferential direction on the peripheral wall of the mud discharge chamber 6 at the front end of the bowl 1. The mud chamber wall 6 and the mud port 7 are configured integrally with the bowl 1 in this embodiment, but are not the basic configuration of the centrifuge, but are configured separately from the bowl 1, Appropriate design changes are possible. The rear end wall 3 of the bowl 1 is provided with a discharge port 8 for the separation liquid c. For example, a plurality of fan-shaped outlets 8 may be provided at regular intervals in the circumferential direction, or a plurality of small holes may be provided concentrically at regular intervals in the rear end wall 3.

  The screw conveyor 10 accommodated in the bowl 1 is attached in a state in which the spiral blade 12 is wound around the outer periphery of the horizontal cylindrical rotary drum 11, and both ends thereof are attached to the bowls of the hollow shafts 4 and 5 of the bowl 1. A rotating shaft 13 that is rotatably supported by the inner protrusion and is inserted through the hollow shaft 4 is rotated with a required speed difference from the bowl 1. A supply chamber 14 for the processing liquid a is provided in the rotary drum 11, and a supply port 15 leading to the annular space 17 between the bowl 1 and the rotary drum 11 is provided on the peripheral wall thereof. A treatment liquid supply pipe 16 inserted through the rear hollow shaft 5 is provided in the supply chamber 14 so as to open.

  A wall 2 is provided at the front end of the annular space 17 of the bowl 1, and a discharge path 20 for the dehydrated cake b <b> 3 is provided in the wall 2. The opening 20a into the bowl of the discharge path 20 is provided in contact with the inner surface of the peripheral wall of the bowl 1, while the opening 20b serving as a discharge port to the outside of the bowl has a height in the radial direction. Therefore, the deposit that can enter the discharge path from the opening 20a is limited to only the lowermost part of the deposited layer. On the other hand, the opening 20b is supplied to such an extent that the processing liquid does not overflow the opening 20b in the initial stage of operation, and determines the initial height of the liquid level in the bowl 1. If the opening 20b is too high, the centrifugal force acting on the dewatered cake in the discharge path 20 cancels out the pressing force acting on the deposited layer in the bowl, thereby reducing the discharge power of the dehydrated cake. It is desirable that it is as low as possible within the required range.

  Further, the separation liquid discharge port 8 defines the liquid level of the annular space 17 during operation, and when the position of the discharge port 8 is lower than the opening 20b, the operation is performed in a so-called "lower overflow" state. When it is high, the operation is in the “upper overflow” state. In the case of the operation in the upper overflow state, the outflow of the processing liquid from the discharge path 20 is blocked by the sediment layer deposited in the vicinity of the opening 20a. In the most extreme case, the separation liquid can be discharged from the axial center.

As shown in FIG. 2, projections 23 and 24 are provided on the outer peripheral surface of the rotary drum 11 of the screw conveyor 10 and the rear end side surface of the spiral blade 12, respectively. Here, the screw conveyor 10 is entirely made of stainless steel, and the protrusions 23 and 24 are fixed by welding. The protrusions 23 and 24 are rectangular parallelepipeds (square column shapes) having a size of about 25 mm × 25 mm × 100 mm, and the protrusions 23 are arranged in a spiral shape (only three in the drawing) with an interval of 50 mm. 24 is arranged at a predetermined radial position from the axial center of the rotating drum 11 on the surface on the rear end side of the spiral blade 12 with an interval of 50 mm. That is, it can be said that the protrusions 24 are also arranged in a spiral shape. Here, the protrusions 23 and 24 are preferably arranged in the vicinity of the front end of the bowl where the sedimented layer b ₂ having a reduced moisture content is consolidated, but the arrangement position may be in front of the supply port 15. . Further, the protrusion 24 may be provided on the surface of the spiral blade 12 on the rear end side of the bowl as shown in FIG. 1 or on the front surface of the bowl.

In the centrifugal separator having the above configuration, the treatment liquid a to be dehydrated enters the supply chamber 14 from the supply pipe 16 as shown by the arrow, and is supplied from the supply port 15 into the annular space 17, and the bowl 1 and the screw conveyor 10. While being separated into a solid and a liquid by the centrifugal force of the rotation, the spiral blade 12 fixed to the outer periphery of the rotary drum 11 of the screw conveyor 10 is conveyed toward the front end in the bowl 1. The separated liquid c, which is the separated liquid, is discharged out of the apparatus from the discharge port 8 on the rear end wall. On the other hand, the sediment layer b ₁ is scraped toward the front end of the bowl 1 by the spiral blade 12 and further subjected to separation action by centrifugal force, so that the separation of the remaining liquid proceeds and is consolidated to decrease the water content. precipitate layer b _2, and the the separated liquid c is also discharged from the discharge port 8. At this time, the protrusions 23 and 24 that are intermittently disposed on the outer peripheral surface of the rotary drum 11 of the screw conveyor 10 and the surface on the rear end side of the spiral blade 12 stir the precipitate layer b ₂ and stay in it. The liquid is released, and at the same time, the precipitation layer b ₂ is pushed away to form a void through which the liquid flows, so that the liquid is guided in the axial direction and in the direction of the discharge port 8. Here, since the projections 23 and 24 are arranged in a spiral shape, the gaps are connected to form a liquid flow path, so that the liquid staying in the precipitation layer b ₂ is efficiently axially and in the direction of the discharge port 8. Led to. Further, the protrusion 24 may be arranged at a certain radial position from the axis of the rotating drum 11, but if the protrusion 24 is arranged so that the radius becomes smaller as it goes in the direction of the discharge port in the spiral blade 12. Since the liquid flow path is connected in the axial direction and in the direction of the discharge port 8, the liquid is more efficiently guided in the axial direction and in the direction of the discharge port 8.

The sedimentation layer b ₂ conveyed to the front part of the bowl 1 is accumulated at the front end of the annular space 17 by a difference from the discharge amount from the discharge path 20. This sedimentary layer has a specific gravity of about 2.5 to 3 if the sedimented heavy component is, for example, sand, and is much heavier than 1 of water. It becomes more than twice as compared with water. Furthermore, if the liquid level determined by the separated liquid discharge port 8 is lower than the rotary drum 11 of the screw conveyor 10 and a space remains between them, the deposited layer rises beyond the liquid level, and its specific gravity Depending on the size and the height of the rise, a large centrifugal head pressure acts in the vicinity of the opening 20a of the discharge path to produce a large consolidation effect on the sedimentary layer. Occurs.

Thus, according to the centrifugal separator according to the present embodiment, the projections 23 and 24 provided in the screw conveyor 10, to form voids in the precipitation layer b _2, staying in the precipitation layer b ₂ By making the liquid easy to flow in the direction of the axial center and the discharge port 8, the centrifugal force acting on the sediment in the sediment layer b ₂ deposited on one end of the bowl 1 is prevented after preventing the water content of the sediment layer b ₂ from decreasing. since only those from the highest part of the compaction effect of the water head pressure is discharged to the bowl out not applied the centrifugal force through the discharge path 20, discharge liquid staying in the precipitation layer b ₂ is mixed in the exhaust cake b ₃ By doing so, it is possible to avoid a situation in which a decrease in moisture content is suppressed. In the above embodiment, as the protrusions 23 and 24, a plurality of rectangular parallelepiped protrusion pieces are intermittently arranged at intervals, thereby facilitating the acquisition and mounting of the constituent members of the protrusion and the liquid flow path. However, the protrusions may be continuously arranged on the outer peripheral surface of the rotating drum 11 and the surface of the spiral blade 12.

In order to demonstrate the effect of the present invention, FIG. 3 is a prototype of a centrifugal separator according to the present invention, the moisture content is measured, and compared with the moisture content of a conventional centrifugal separator. Here, the prototype centrifuge has projections 23 and 24 as shown in FIGS. 1 and 2, and the conventional device has no projections, and has the same configuration and specifications except for the presence or absence of the projections. (Standard treatment amount: 1 m ³ / h, power: main motor 5.5 kW, treated sludge: digested sludge). Also, the centrifugal effect of the horizontal axis in FIG. 3 (G) is a G = Nr ^2/895. Here, r is the radius of the bowl 1 and N is the number of rotations of the bowl 1.

  From FIG. 3, in the case of a conventional apparatus without protrusions, when the centrifugal effect is increased by increasing the number of revolutions, the decrease in the moisture content of the cake tends to reach a peak, whereas the embodiment apparatus having protrusions In this case, in the whole area measured (G = 1000-2500), the moisture content is lower than that of the conventional device, and the decrease in the moisture content has peaked even in the region where the consolidation effect is high and the centrifugal effect is high (G = 2500). It was confirmed that there was no tendency.

It is a longitudinal cross-sectional view of the axial center direction of the centrifuge which concerns on embodiment of this invention. It is a perspective view of the screw conveyor in the embodiment of the present invention. It is a figure which shows the measurement result of the moisture content of the Example of this invention, and a conventional apparatus. It is a longitudinal cross-sectional view of the axial center direction of the conventional decanter type centrifuge.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Bowl, 10 ... Screw conveyor, 11 ... Rotary drum, 12 ... Spiral wing, 23, 24 ... Protrusion.

Claims (2)

A cylindrical bowl that rotates in one direction, and a screw conveyor that rotates in the same direction in the bowl, coaxially with the bowl and rotating in the same direction, and is fed into the rotating bowl The heavy components are separated from the processing liquid by centrifugal force, conveyed to one side of the bowl by the screw conveyor and accumulated, pushed out from the heavy component discharge port provided on the one side, and the separated liquid is separated from the other of the bowl. In the centrifugal separator that is to be discharged from the separation liquid outlet provided on the side,
Protrusions are provided on the one or other surface of the spiral wing of the screw conveyor, or on the outer peripheral surface of the rotating drum of the screw conveyor, and the liquid staying in the heavy component is directed toward the separated liquid discharge port. Centrifugal separator characterized by escape. The centrifuge according to claim 1,
A centrifugal separator characterized by arranging the protrusions in a spiral shape.

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