GB2386575A

GB2386575A - Cyclone with permeable wall

Info

Publication number: GB2386575A
Application number: GB0302482A
Authority: GB
Inventors: John Stirling Sexton; Andrew Spencer Bevis
Original assignee: Porvair Filtration Group Ltd; Microfiltrex Ltd
Current assignee: Porvair Filtration Group Ltd
Priority date: 2002-02-04
Filing date: 2003-02-03
Publication date: 2003-09-24
Anticipated expiration: 2023-02-03
Also published as: GB0202554D0; GB2386575B; GB0302482D0

Abstract

A centrifugal separator 2 comprises a chamber 4 defined by a chamber wall 6, which has a tapered cross-section. The separator 2, has a fluid inlet 8, a first fluid outlet 10, a second fluid outlet 12 and a third fluid outlet. The third fluid outlet is provided by permeable material of the chamber wall 6. Suitable materials for use in the permeable wall are sintered metal, sintered ceramics or sintered/moulded polymers.

Description

IMPROVEMENTS IN AND RELATING TO SEPARATORS

The present invention relates to separators in particular, although not exclusively to centrifugal separators.

It is well known to use centrifugal forces to separate heavier or more dense 5 materials from a less dense carrier fluid. Generally, centrifugal separators, also known as cyclone separators, use centrifugal forces to spin heavier materials to an outer wall of the separator and displace the carrier fluid to the centre of the cyclone. The carrier fluid is often air or a liquid.

A conventional centrifugal separator generally comprises a chamber having an 10 inlet and two outlets, which outlets are generally known as an overflow and an underflow. The chamber is defined by a wall and may have a cylindrical or tapered, generally substantially conical, profile. The first outlet is suitably located at the bottom of the chamber, substantially at the centre longitudinal axis of the chamber. The second outlet is usually located at the top of the chamber, in the region of the centre 15 longitudinal axis of the chamber. Suitably, the first and second outlets are arranged opposite one another, on the same longitudinal axis.

If the chamber is tapered, it is generally arranged to taper inwards from the top to the bottom. The inlet is usually located at the wider end of the chamber, and is generally arranged tangentially orientated, substantially transverse of the centre 20 longitudinal axis of the chamber. An overflow outlet is located at the wider end of the chamber and an underflow outlet is located at the narrower end of the chamber.

In use of a conventional centrifugal separator, fluid enters the chamber through the inlet. The tangential line of approach through the inlet causes the fluid to spin downwards through the chamber, providing a primary vortex within the chamber, 25 which effect is enhanced if the chamber is tapered. The decreasing diameter of a tapered chamber causes the tangential velocity of the fluid to increase as it passes downwards through the chamber.

The spinning motion of the fluid causes the more dense materials therein to be displaced to the wall of He chamber. At a particular diameter of the chamber a 30 secondary vortex is formed moving in a direction reverse to the primary vortex, which

is generally upwards through the chamber. The secondary vortex passes through the centre of the chamber, substantially along the centre longitudinal axis of the chamber.

The more dense materials separated from the fluid by the primary vortex collect at the bottom of the chamber and are discharged from the chamber via the 5 underflow outlet. The secondary vortex comprising carrier fluid with reduced contaminants, discharges through the overflow outlet.

Although a conventional centrifugal separator can be used to separate more dense materials from less dense materials (which include a less dense carrier fluid), such a separator is not absolutely effective. The carrier fluid discharged in the 10 secondary vortex will generally still comprise some of the more dense contaminant.

It is an object of preferred embodiments of the present invention to provide an improved separator.

The present invention provides a centrifugal separator comprising a chamber defined by a chamber wall, a fluid inlet, a first fluid outlet, a second fluid outlet and a 15 third fluid outlet, the chamber having a tapered profile and the third fluid outlet being provided by permeable section of the chamber wall.

Suitably, the permeable section of the chamber wall comprises a permeable material. Preferably, the permeable section comprises a substantial portion of the chamber wall. More preferably, the permeable section comprises substantially the 20 whole, and more preferably the whole, of the chamber wall.

The permeable material may comprise any suitable material. Suitably, the permeable material comprises a porous material. Suitable porous materials include, for example, sintered metals, such as stainless steel, sintered ceramic, sintered and/or moulded polymers, or mixtures thereof. The porous material used to make the 25 permeable material may be in any suitable form, including in the form of a slurry, a powder, fibres, wires, homogenous sheet or mixtures thereof.

The third fluid outlet may be known as a permeate.

Suitably, part at least of the chamber is tapered. Suitably, substantially the whole of the chamber is tapered. Preferably, the chamber tapers from the inlet to the 30 first fluid outlet. Suitably, substantially the whole, and preferably the whole, of the chamber has a circular, or substantially circular, transverse, internal cross-sectional shape. Suitably, when arranged for use, the widest section of the chamber is located at

the top of the device and the chamber tapers inwardly and uniformly downwards to the narrowest section of the chamber.

Preferably, the permeable section of the chamber wall is provided only in the tapered section of the chamber. Suitably, the permeable section provides the chamber 5 wall of substantially the whole, and preferably the whole, of the tapered section of the chamber. A centrifugal separator in accordance with the present invention may have any other feature present in a conventional centrifugal or cyclone separator. Suitably, the fluid inlet and the first and second fluid outlets of the separator are arranged relative to 10 the chamber in the same manner as a fluid inlet, an underflow and an overflow of a conventional centrifugal separator. The first fluid outlet is suitably an underflow, as referred to above and the second fluid outlet is suitably an overflow, as referred to above. The fluid inlet may be provided by an inlet conduit that extends from an inlet 15 opening in a wall of the chamber. The inlet conduit is suitably aligned to have a tangential interface with the interior of the chamber. The inlet opening is suitably located in a side wall of the chamber. Suitably the inlet opening is located at the widest section of the chamber. The inlet opening is preferably at the top of the chamber, when arranged for use.

20 The second outlet is suitably provided by an outlet conduit extending into the chamber. The second outlet conduit preferably extends through the top wall of the chamber. The second outlet conduit is suitably located at substantially the centre of the chamber and preferably extends substantially parallel to the longitudinal axis of the chamber. The second outlet conduit may extend beyond the inlet opening into the 25 chamber. The first outlet is suitably provided by an opening in the chamber wall at the narrowest section of the chamber. The first outlet may extend across part of the width of the chamber. Suitably, the first outlet extends across substantially the full, width of the chamber. Preferably, the first outlet extends across the full cross-sectional area of 30 the chamber. Preferably, the first outlet is located at the bottom ofthe chamber, in use.

The permeable material facilitates flow of fluid from the chamber to the exterior of the chamber wall as a result of the pressure difference between the interior

of the chamber and the exterior of the chamber wall. The spiralling action of the fluid within the chamber prevents the interior surface of the permeable material from becoming covered by separated material of higher density, and thus prevents blockage of pores within the permeable material by said separated material.

5 A separator in accordance with the present invention advantageously generates three emission streams. The first emission stream comprises substantially the more dense material and a small amount of carrier fluid or less dense material, which is discharged from the separator via the first outlet. The first emission stream is commonly known as the high emission stream. The second emission stream comprises 10 substantially less dense material and comprises substantially more carrier fluid containing significantly less of the more dense material than upon entry into the separator, which second emission stream is discharged from the second outlet. The second emission stream is commonly known as the low emission stream. The third emission stream comprises a substantially pure fluid, which is discharged from the 15 separator via the permeable material of the permeable secion of the chamber wall. The third emission stream is herein defined as the permeate emission stream.

The first and/or second emission stream may require further separation or filtration to effect further separation or purification.

A centrifugal separator in accordance with the present invention can 20 advantageously handle a greater flow rate than a conventional centrifugal separator, because a separator according to the present invention is able dissipate greater input flow as a result of the additional outlet.

The present invention will now be described, by way of example only, with reference to the following drawing, in which: Figure 1 is a schematic cross-sectional side view of a separator, and Figure 2 is a plan view of the separator of figure 1.

The separator 2 of figure 1 comprises a chamber 4 defined by a chamber wall 30 6. The chamber 4 has a conical cross-sectional shape that tapers inwards from the top to the bottom. The whole of the chamber wall 6 comprises a permeable material as stated earlier.

s The separator 2 further comprises an inlet, generally designated by reference numeral 8, an underflow 10 and an overflow 12.

The inlet 8 comprises a tube 14 extending from the chamber wall 6 arranged tangentially thereof (as can be seen clearly in figure 2). The inlet 8 has an inlet 5 opening 18 aligned with the top of the chamber 4, which opening 18 extends across the full cross-sectional area of the top of the chamber 4. The inlet opening 18 is provided by a section of the chamber having a generally cylindrical transverse internal cross-

sectional shape.

The underflow 10 comprises a conduit 20 extending from the bottom of the 10 tapered chamber 4. The underflow 10 as provided by the conduit 20 extends across the full cross-sectional area of the bottom end of the chamber 4.

The overflow 12 is provided by a conduit 22, which extends through the tube 14. The conduit 22 is arranged substantially perpendicular to the body 14. The conduit 22 is aligned substantially with the centre longitudinal axis A of the chamber 15 4. In use of the separator 2 illustrated in figure 1, fluid is fed into the separator through the tube 14 and opening 18, as indicated by arrow P. As the fluid passes downwards through the chamber 4, it is caused to spin because of the tangential positioning of the inlet 14, the generally cylindrical interior crosssectional shape of 20 the chamber at the inlet opening 18 and the decreasing diameter of the chamber 4.

Arrows Q indicate the spinning movement of the fluid forming a primary vortex. The spinning movement of the fluid will cause more dense material in the fluid to be pushed to the chamber wall 6. The more dense material (not shown) will traverse spirally through the chamber 4 and be discharged from the separator 2 through the 25 underflow 10, as indicated by Arrow R. Upon reaching the bottom of the chamber 4, the less dense material and/or the cattier fluid will form a secondary vortex (not shown) travelling in the reverse direction compared to the primary vortex (i.e. upwards through the chamber). The less dense material and/or carrier fluid forming the secondary vortex will exit the separator 30 2 via the overflow 12 as indicated by Arrow S. The secondary vortex will also comprise some of the more dense material that has not been successfully separated from the less dense material andlor carrier fluid.

The permeable chamber wall 6 allows pure fluid to be separated Mom the more dense material. The pure fluid will pass through the permeable chamber wall 6 as indicated by Arrows T.

Claims

1. A centrifugal separator comprising a chamber defined by a chamber wall, a fluid inlet, a first fluid outlet, a second fluid outlet and a third fluid outlet, the chamber having a tapered profile and the third fluid outlet being 5 provided by permeable section of the chamber wall.

2. A separator according to claim 1, wherein the permeable section comprises a permeable material.

3. A separator according to claim 1 or 2, wherein substantially the whole of the chamber wall comprises a permeable material.

10

4. A separator according to any one of the preceding claims, wherein substantially the whole of the chamber has a tapered profile.

5. A separator according to any one of the preceding claims, wherein the inlet is located at the widest section of the tapered section of the chamber.

6. A separator according to claim 6, wherein the widest section of the tapered 15 section of the chamber is the top end of the chamber, when in use.

7. A separator according to any one of the preceding claims, wherein the first outlet is located at the narrowest section of the tapered section of the chamber.

8. A separator according to claim 8, wherein the narrowest section of the 20 tapered section of the chamber is at the bottom end of the chamber, when in use.

9. A separator according to any one of the preceding claims, wherein the first outlet is located below the second outlet, when in use.

10. A separator according to any one of claims l-9, wherein, in use, the second 25 outlet is located below the first outlet.

11. A separator according to any one of claims 1-9, wherein, in use, the first outlet and the second outlet lie in the same horizontal plane.

12. A separator according to any one of the claims 2-11, wherein the permeable material is sintered metal, sintered ceramic, sintered andlor moulded 30 polymers, or mixtures thereof.

13. A separator according to any one of the preceding claims, wherein the inlet is provided by a tangentially arranged inlet conduit.

14. A separator substantially as described herein, with reference to the drawing hereof.