HK1142027B - A centrifugal separator and a liquid phase discharge port member - Google Patents

Description

Centrifugal separator and liquid phase discharge port member

[ technical field ] A method for producing a semiconductor device

The invention relates to a centrifugal separator comprising: a drum (bowl) rotating in use about an axis of rotation extending in a longitudinal direction of the drum; a base plate disposed at one longitudinal end of the drum, the base plate having an inner side and an outer side; an exit aperture disposed in the base plate; a housing protruding at an outlet hole on an outer side of the base plate, the housing including a housing side whose normal line extends at an acute angle to a circumferential direction of a drum at the housing; and a discharge hole provided in the case side.

[ background of the invention ]

A centrifugal separator of this type is known from US 2004072668, which describes a housing with a nozzle arranged in the housing side. Above the housing, i.e. closer to the longitudinal axis, a weir (weir) may be provided. The depth of the liquid pool in the drum is determined by the diameter of the nozzle, assuming that the feed speed to the separator is constant.

Another such centrifugal separator is known from US 7022061, which describes a liquid phase discharge port having a tubular member with an elbow.

US-A-4575370 discloses A centrifugal separator having A rotating drum with A base plate and A liquid phase outlet hole provided in the base plate. The outlet opening is partially covered by a weir to adjust the level or depth of the liquid pool in the bowl. In general, the use of a weir ensures that the liquid level in the drum is substantially unlikely to exceed the level of the weir, since the area of the holes above the weir is infinite from a practical point of view. According to US-A-4575370, A notch is provided in the overflow edge of the weir or A through hole is provided in the weir, so that during the start-up phase of running the separator it is possible to obtain operation with A lower liquid level at A lower feed rate to the separator.

One problem in such centrifugal separators is that the liquid flowing over the overflow edge of the weir plate tends to adhere to the outside of the base plate and thus to be accelerated, which consumes energy and thus energy losses and thus power up to 15% in addition. Furthermore, after entering the drum, the feed is accelerated to a rotational speed and the energy thus consumed is lost when the liquid phase leaves the weir at the outlet in the substrate.

The separator of US 2004072668 mentioned above attempts to solve this problem. However, the use of a nozzle with a given diameter makes it necessary for the liquid level in the drum to change also when the feed speed is changed.

[ summary of the invention ]

The present invention therefore aims to provide a centrifugal separator in which the above-mentioned problems are eliminated or reduced.

According to a first aspect of the invention this object is achieved by providing a centrifugal separator of the technology mentioned in the first paragraph, wherein the discharge opening is defined radially outwardly by a weir with an overflow edge, and said discharge opening extends radially inwardly to a position above a highest expected liquid level in the drum.

The arrangement of the weir at the discharge orifice ensures that the liquid level in the drum remains substantially constant at all feed speeds, since the discharged liquid flows only over the top of the weir plate, which thus determines the liquid level in the enclosure and thus in the drum. Moving the drain hole and weir away from the outlet hole ensures that no liquid will adhere to the outside of the substrate. Thus energy losses in the range of 10% to 15% can be avoided. Further, when the liquid is discharged in the opposite direction with respect to the rotating direction, the energy of the rotating liquid can be regained at the discharge holes, thereby generating a power increase in the range of 10% to 15%.

Typically, several outlets are provided in the base plate, which are arranged equidistantly on a common radius.

According to a preferred embodiment of the invention, the acute angle is in the range between 0 ° and 60 °, preferably between 5 ° and 35 °, and more preferably between 15 ° and 30 °. An acute angle of 0 ° or close to 0 ° will provide maximum energy recovery. However, if multiple outlets are provided with housings protruding from the base plate of the drum, a 0 ° angle may result in liquid discharged from one outlet colliding with an adjacent housing protruding from the base plate of the drum. This is avoided by providing a larger angle. If only a few outlets, for example two outlets, are provided, no collision problems exist.

According to a particularly preferred embodiment of the invention, the weir comprises a hole. By providing A liquid outlet that is effective at start-up conditions with A low feed rate to provide A low liquid level in the drum, said holes prevent liquid from flowing out of the drum through the solids discharge hole during start-up, as is generally known from the above-mentioned US-A-4575370.

According to a preferred embodiment of the invention, the weir is provided as a replaceable weir plate, whereby the level of the overflow edge can be changed to correspond to the desired liquid level in the drum. According to a further preferred embodiment of the invention grooves are provided in the discharge opening, which grooves are adapted to receive the weir plate. The process of replacing the slice is considerably facilitated and correct installation of the slice is always ensured.

According to another preferred embodiment of the invention, the housing comprises a curved wall extending from the base plate to the far side of the housing side, the side of the discharge hole being flush with the curved wall. Such a configuration provides an inner surface of the housing that causes little turbulence in the discharged liquid, thereby further reducing power consumption.

According to a further preferred embodiment of the invention, the curved wall and the shell side intersect at substantially right angles.

According to a second aspect of the invention, this object is achieved by a liquid phase discharge port member adapted to be arranged on an outlet hole of a drum of a centrifugal separator, said liquid phase discharge port member comprising: a flange; an inlet aperture disposed in the flange; a housing projecting at an inlet aperture on one side of the flange, the housing comprising a housing side, a normal to the housing side extending at an acute angle relative to the flange; and a discharge orifice provided in the shell side, the liquid phase discharge port member being characterized in that the discharge orifice is defined by a weir having an overflow edge.

Further preferred embodiments of providing the liquid phase discharge means with the above-mentioned advantages emerge from the dependent claims 9 to 14.

With the liquid phase discharge port member according to the invention it is possible to adapt existing centrifugal separators to achieve the above mentioned advantages by merely attaching the liquid phase discharge port member according to the invention to the liquid phase outlet port of the separator.

Preferably, the flange of the liquid phase discharge port member includes a hole adapted to receive fastening means such as a bolt.

[ description of the drawings ]

The invention will now be described in more detail on the basis of non-limiting exemplary embodiments and with reference to the accompanying drawings. In the drawings, there is shown in the drawings,

fig. 1 shows a schematic view of a centrifugal separator of the prior art;

fig. 2 shows a front view of a prior art outlet hole of a centrifugal separator, which outlet hole is provided with a weir plate;

FIG. 3 shows a cross-section along the line III-III in FIG. 2;

FIG. 4 shows a perspective view of a liquid phase discharge port member according to the present invention;

fig. 5 shows a perspective top view of the liquid phase discharge port member according to fig. 4;

FIG. 6 shows a top view of the liquid phase drain port member;

FIG. 7 shows a front view of a liquid phase discharge port member positioned on a base plate of the centrifugal separator; and

fig. 8 shows a rear view of the liquid phase discharge port member.

[ detailed description ] embodiments

The prior art centrifugal separator 1 shown in fig. 1 comprises a bowl 2 and an auger 3, which are mounted on a shaft 4 such that, in use, they can be rotated about an axis of rotation 5, the axis of rotation 5 extending in the longitudinal direction of the bowl 2. Furthermore, the centrifugal separator 1 has a radial direction 5a extending perpendicular to the longitudinal direction.

For simplicity, the directions "up" and "down" used herein refer to a radial direction toward the rotation axis 5 and a radial direction away from the rotation axis 5, respectively.

The drum 2 comprises a base plate 6 arranged at one longitudinal end of the drum 2, which base plate 6 has an inner side 7 and an outer side 8. The base plate 6 is provided with a plurality of liquid phase outlet holes 9. The rotary drum 2 is provided with a solid phase discharge hole 10 at one end opposite to the substrate 6.

Furthermore, the screw conveyor 3 comprises an inlet opening 11 for feeding, for example, a slurry comprising a light or liquid phase 12 and a heavy or solid phase 13 to the centrifugal separator 1. During the rotation of the centrifugal separator 1 as described above, a separation of the liquid phase 12 and the solid phase 13 is obtained. The liquid phase 12 is discharged through the outlet opening 9 in the base plate 6, while the screw conveyor 3 conveys the solid phase 13 towards the solid phase discharge opening 10, through which solid phase 13 is finally discharged.

With reference to fig. 2, each liquid phase outlet opening 9 may be partially covered by a weir plate 14 according to the prior art. The weir plate 14 determines a liquid level 15 (see fig. 3) in the drum, which level 15 is substantially impossible to exceed the weir plate's overflow edge 17, because the area 16 of the hole above the weir plate 14 is infinite from a practical point of view of the liquid. The weir plate 14 is securely fixed to the base plate 6 by fastening means (not shown) in the form of e.g. bolts, which protrude through holes 18 in the peripheral part 19 of the support means 21. In the fixed state, the peripheral portion 19 covers at least a part of the peripheral edge 20 of the liquid phase outlet opening 9, and the support means 21 partly covers the weir plate 14 to a level indicated at 22 on fig. 2.

Fig. 3 shows a cross section through the liquid phase outlet opening 9 along the line III-III in fig. 2, indicating a liquid level 15, which substantially coincides with the overflow edge 17 of the weir plate 14.

One problem in the prior art relates to the tendency of liquid flowing over the overflow edge 17 of the weir plate to adhere to the outer surface of the base plate 6 as it is caught by the support means 21, which results in additional power consumption.

To overcome this drawback, the centrifugal separator 1 may according to the invention be provided with a liquid phase discharge port member arranged on the outlet hole 9 of the drum 2 of the centrifugal separator 1 instead of the weir plate 14 and its support device 21.

One embodiment of the liquid phase discharge port member 30 is shown from different perspectives in fig. 4 to 8, and is therefore described below as an exemplary but by no means limiting embodiment of the invention.

With particular reference to fig. 4 and 5, the liquid phase discharge port member 30 includes a flange 31 in which an inlet hole 32 (best seen in fig. 8) is provided, and a housing 33 protruding at the inlet hole 32 on one side of the flange 31. The housing 33 comprises a housing side 34, wherein a normal 35 (shown on fig. 6) of the housing side 34 extends at an acute angle β (also shown on fig. 6) with respect to the flange 31. In the shell side 34, a discharge opening 36 is provided, which is delimited by a weir consisting of a weir plate 45 with an overflow edge 39.

In the mounted position, the overflow edge 39 has a substantially constant distance from the axis of rotation 5 of the centrifugal separator 1. This is indicated in fig. 7 by a radius 46, which radius 46 is perpendicular to the overflow edge 39 and which radius comprises an arrow 47 pointing towards the axis of rotation of the centrifugal separator.

With this configuration, the liquid level in the bowl 2 of the centrifugal separator 1 is determined by the level of the overflow edge 39 of the weir plate 45. Thus, the liquid level in the drum 2 can be kept substantially constant at all feed speeds.

According to a preferred embodiment, the above-mentioned acute angle β is in the range between 0 ° and 60 °, preferably between 5 ° and 35 °, and more preferably between 15 ° and 30 °, for example about 25 ° as shown.

In the illustrated embodiment, the liquid phase drain port member 30 includes a hole 37, which hole 37 provides an additional liquid outlet below the overflow edge 39. This additional liquid outlet may be provided in A manner known per se for operating the centrifugal separator at A low liquid level in the drum 2 during the start-up phase (cf. US-A-4575370).

The weir plate 45 is replaceable in this embodiment, and in order to easily replace the weir plate 45, a groove 38 is provided at the discharge hole 36, the groove 38 being adapted to receive the weir plate 45 fixed by screws 50. With this configuration, the level of the overflow edge 39 can be varied in a simple manner to correspond to the desired level in the drum 2.

In the figures, the shell side 34 is shown as including an upper transverse portion 44. However, the purpose of this transverse portion 44 is merely to support the housing 33, and this transverse portion 44 can thus be omitted if the strength of the housing 33 and the rest of the housing side 34 is sufficient on its own to withstand the pressure from the liquid without deforming.

The housing 33 comprises a curved wall 49 extending from the flange 31 to the distal side 40 of the housing side 34, wherein the side 43 of the discharge hole 36 is flush with the curved wall 49. This configuration is provided for the inner surface 41 of the housing to cause little or no turbulence in the discharged liquid. The curved wall 49 and the housing side 34 intersect at substantially a right angle.

Further, the through hole 42 is preferably provided in the flange 31. The through hole 42 may be used to fix the liquid phase discharge port member 30 to the base plate 6 of the centrifugal separator 1 by using fastening means (not shown) such as bolts or the like.

The top of the housing is open in the embodiment shown. The housing may be closed by a top wall, but such a top wall will be superfluous, at least from the flow point of view, since the liquid phase leaving the drum 2 via the outlet opening 9 will flow out via the lower part of the discharge opening 36 directly above the overflow edge 39 without filling the upper part of the discharge opening 36.

In an alternative embodiment of the invention the housing is formed integrally with the base plate of the centrifugal separator, instead of being attached thereto by means of the flange 31. By contrast to the embodiments described above, in such alternative embodiments, the outlet aperture of the base plate would be the same as the inlet aperture of the housing.

The centrifugal separator equipped with the liquid phase discharge port member 30 works as follows:

the bowl 2 and the screw conveyor 3 are caused to rotate in the same direction but at different rotational speeds about their common axis of rotation 5. A substance comprising a liquid phase 12 and a solid phase 13 is fed into the drum via inlet port 11. The solid phase 13 will be separated from the liquid phase 12 and carried towards the solid phase discharge orifice 10 due to the difference in rotational speed. At the same time, the liquid phase flows toward the outlet hole 9 in the base plate 6, and is discharged therefrom through the liquid phase discharge port member 30. Due to the rotation of the drum 2, the liquid phase discharge port member 30 will move in the direction indicated by the arrow 48 (fig. 7).

It should be noted that for a centrifuge with opposite rotational directions, the liquid phase discharge port member should be mirror-inverted with respect to the radius.

The discharge holes 36 of the liquid phase discharge port member 30 are arranged such that they face rearward with respect to the rotational direction 48, whereby the liquid phase is discharged in a substantially circumferential direction opposite to the rotational direction.

The liquid phase fills the lower portion of the housing 33 and flows over the overflow edge 39. The curved shape of the casing 33 and the flush transition between the casing 33 and the casing side 34 ensure a smooth flow of liquid through the casing 33, whereby the liquid phase leaves the casing in the direction of the normal 35.

The liquid phase is then discharged through the discharge orifice 36, the flow profile rising slightly above the overflow edge 39. During the start-up phase, the liquid level 15 is below the overflow edge 39, and the liquid phase can be discharged through the holes 37 in the weir plate as described above. At full speed operation, between 30% and 70%, for example, about 50% of the liquid phase may be discharged through the holes 37. Depending on the feed to be processed in the centrifuge, it may be preferred to provide only some of the weir plates with holes. It is thus possible to provide a smaller number of larger holes with less tendency to clog, which together have the same capacity as the smaller holes provided in the weirs.

The weir plate 45 and thus the overflow edge 39, together with their orientation at an acute angle β (see fig. 6) in the housing 33, thereby lifting them from the base plate 6, ensures that when the liquid flows past the overflow edge, it neither adheres to the outside of the base plate 6 of the drum 2 nor interferes with the adjacent liquid phase discharge port 30 arranged at the adjacent outlet opening 9 in the base plate 6, but is discharged only in such a way that it leaves substantially little or no residue on the base plate 6 or the liquid phase discharge port 30.

The overflow edge 39 ensures a substantially constant liquid level in the drum 2 even at varying feed rates.

It should be noted that the above description of preferred embodiments is only an example and that a person skilled in the art will understand that many variations are possible without departing from the scope of the claims. In the case of centrifugal separation of, for example, two liquid phases, it is possible to use the liquid phase discharge port member according to the invention at the outlet for only one of the liquid phases or for both.

Claims (18)

1. A centrifugal separator (1) comprising:

a drum (2) which, in use, rotates about an axis of rotation (5) extending in the longitudinal direction of the drum;

a radial direction (5a) extending perpendicular to the longitudinal direction;

a base plate (6) arranged at one longitudinal end of the drum, the base plate having an inner side (7) and an outer side (8);

an outlet aperture (9) provided in the base plate;

a housing (33) protruding at an outlet aperture on an outer side of the base plate;

the housing comprises a housing side (34), a normal (35) of which extends at an acute angle (β) with respect to a circumferential direction of the drum at the housing; and

a discharge hole (36) provided in the housing side,

wherein the drain is defined radially outwardly by a weir (45) with an overflow edge (39), and the drain extends radially inwardly to a position above a highest expected liquid level of the bowl.

2. A centrifugal separator according to claim 1, wherein the acute angle is in the range between 0 ° and 60 °.

3. A centrifugal separator according to claim 1 wherein the acute angle is between 5 ° and 35 °.

4. A centrifugal separator according to claim 1 wherein the acute angle is between 15 ° and 30 °.

5. A centrifugal separator according to any one of claims 1 to 4, wherein the weir comprises an aperture (37).

6. A centrifugal separator according to any one of claims 1 to 4 wherein the weir is provided by a replaceable weir plate.

7. A centrifugal separator according to claim 6, wherein the trough (38) provided in the discharge hole is adapted to accommodate the slice.

8. A centrifugal separator according to any one of claims 1-4, wherein the housing comprises a curved wall (49), which curved wall (49) extends from the base plate to the distal side (40) of the housing side, the discharge hole being flush with one side of the curved wall.

9. A centrifugal separator according to claim 8 wherein the curved wall and the housing side intersect at substantially right angles.

10. A liquid phase discharge port member (30) adapted to be arranged on an outlet hole (9) of a drum (2) of a centrifugal separator (1), comprising:

a flange (31);

an inlet aperture (32) disposed in the flange;

a housing (33) protruding at an inlet hole on one side of the flange;

the housing comprises a housing side (34), a normal (35) of the housing side extending at an acute angle (β) with respect to the flange; and

a discharge hole (36) provided in the housing side,

wherein the discharge orifice is defined by a weir (45) with an overflow edge (39).

11. A liquid phase discharge port member according to claim 10, wherein said acute angle is in a range between 0 ° and 60 °.

12. A liquid phase discharge port member according to claim 10, wherein said acute angle is between 5 ° and 35 °.

13. A liquid phase discharge port member as claimed in claim 10, wherein said acute angle is between 15 ° and 30 °.

14. A liquid phase discharge port member according to any one of claims 10 to 13, wherein said weir includes a hole (37).

15. A liquid phase discharge port member as claimed in any one of claims 10 to 13, wherein said weir is provided by a replaceable weir plate.

16. A liquid phase discharge port member as claimed in claim 15, wherein a groove (38) provided at said discharge hole is adapted to accommodate said weir plate.

17. A liquid phase discharge port member according to any one of claims 10 to 13, wherein said housing includes a curved wall (49), said curved wall (49) extending from said flange to a distal side (40) of said housing side, one side (43) of said discharge hole being flush with said curved wall.

18. A liquid phase discharge port member as claimed in claim 17, wherein said curved wall and said shell side intersect at substantially a right angle.