WO2007094727A1

WO2007094727A1 - Centrifugal separator

Info

Publication number: WO2007094727A1
Application number: PCT/SE2007/050016
Authority: WO
Inventors: Claes-Göran Carlsson; Jan Skoog; Tommy Myrvang
Original assignee: Alfa Laval Corporate Ab
Priority date: 2006-02-13
Filing date: 2007-01-12
Publication date: 2007-08-23
Also published as: SE529608C2; SE0600313L

Abstract

The invention refers to a centrifugal separator for cleaning of a gas containing liquid impurities. The centrifugal separator comprises a rotating member (4), which is provided in a separation space (2) defined by a casing (1). The rotating member is adapted to bring the gas to rotation in a direction (r) of rotation for separating at least a main part of the liquid impurities from the gas. A gas outlet (10) for the cleaned gas is provided downstream the rotating member. A disc (30) is provided between the rotating member and the gas outlet. The disc is provided with a number of through-flow openings (31 ) which each comprises a tongue (32) projecting from an edge of the through-flow opening. The tongue is located upstream the disc.

Description

Centrifugal separator

THE BACKGROUND OF THE INVENTION AND PRIOR ART

The present invention refers generally to a centrifugal separator for cleaning of gases from liquid impurities such as oil particles and oil mist. More specifically, it is aimed at a centrifugal separator for cleaning of a gas containing liquid impurities, according to the preamble of claim 1.

Such a centrifugal separator is disclosed in SE-C-524 139. In this known centrifugal separator, the tongues on the disc are provided to be located downstream the disc. By means of the disc and the arranged tongues, a pressure recovering deceleration of the tangential flow velocity of the gas is obtained. The tangential flow may then to a substantial part be converted to a substantially axial flow with a relatively low flow velocity and high drive pressure. In such a way, the flow of gas through the centrifugal separator may be increased.

SUMMARY OF THE INVENTION

The object of the present invention is to propose an alternative technical solution to the above-described known technique. A further object is to provide a technical solution which results in a better effect than the above described technical solution. In particular, it is aimed at an increased gas flow through the centrifugal separator.

This object is achieved by the centrifugal separator initially defined, which is characterized in that the tongue projects from the edge in such a way that the tongue is located upstream the disc.

By means of such tongues, an efficient conversion of the tangential gas flow to a substantially axial gas flow downstream the disc is achieved. The solution according to the invention permits an effi- cient increase of the gas flow through the centrifugal separator. In such a way, the efficiency of the centrifugal separator may be further improved. The applicant has during experiments arrived at the conclusion that the gas flow by means of such tongues provided upstream the disc becomes larger than according to the technique disclosed in SE-C-524 139. The result of these investigations is illustrated in the attached Fig. 4.

According to an embodiment of the invention, the tongues project from the respective edge towards the direction of rotation. Consequently, the tongues will function as guide vanes guiding the tangential gas flow in through the through-flow openings. Furthermore, the tongues may be inclined from the disc towards the rotating member.

According to a further embodiment of the invention, the through- flow openings have a substantially arched extension in the direction of rotation. Advantageously, also the tongues have such a substantially arched extension in the direction of rotation. Such a design of the openings and the tongues has an advantageous influence on the gas flow.

According to a further embodiment of the invention, the disc is substantially planar and parallel with a cross-sectional plane through the centrifugal separator. Advantageously, the axis of rotation forms the normal to the cross-sectional plane. It is to be noted, that the disc also may be somewhat arched or have, for instance, a slight conical shape.

According to a further embodiment of the invention, the tongues are inclined with an angle of inclination in relation to the cross-sectional plane, wherein the angle of inclination is between 1° and 40°.

According to a further embodiment of the invention, the disc is ar- ranged in such a way that substantially all gas flowing from the inlet to the gas outlet is conveyed through the through-flow opening. According to a further embodiment of the invention, the disc comprises at least three such through-flow openings provided with such a respective tongue. It is to be noted, that the disc also could comprise merely two through-flow openings with such a respective tongue or four, five, six or more through-flow openings with such a respective tongue.

According to a further embodiment of the invention, the rotating member comprises a number of separating discs.

According to a further embodiment of the invention, the centrifugal separator is arranged to be provided in such a way that the axis of rotation extends substantially vertically, wherein the stationary casing has an upper end and a lower end and wherein the gas outlet is disposed at the upper end. By such a design, the tongues may thus be arranged to be inclined downwardly from the disc.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is now to be explained more closely through a description of various embodiments and with reference to the drawings attached hereto.

Fig. 1 discloses a vertical section through a centrifugal separa- tor according to the invention.

Fig. 2 discloses a horizontal cross-section through the centrifugal separator in Fig. 1.

Fig. 3 discloses a cross-sectional view through a disc of the centrifugal separator along the line Ill-Ill in Fig. 2. Fig. 4 discloses a diagram of the flow as a function of the number of revolutions of the centrifugal separator according to the invention in comparison with centrifugal separators according to prior art. DETAILED DESCRIPTION OF VARIOUS EMBODIMENTS OF THE INVENTION

Fig. 1 discloses a centrifugal separator for cleaning of a gas con- taining liquid impurities, for instance oil in the form of oil mist or oil particles, and possibly solid particles. The centrifugal separator comprises a stationary casing 1 , which encloses a substantially closed separation space 2. The casing has an inner wall surface 3 which faces the separation space 2. The separation space 2 is ar- ranged to permit the gas to flow therethrough.

The centrifugal separator further comprises a rotating member 4, which is provided in the separation space 2 and arranged to rotate in a direction r of rotation around an axis x of rotation, which also forms a centre axis through the casing 1. The centrifugal separator is provided in such way that the axis x of rotation extends substantially vertically so that the stationary casing 1 has an upper end Y and a lower end 1 ".

The rotating member 4 comprises a spindle member 5, which is journalled in the casing 1 at the upper end Y by means of a bearing 6, and a number of separating discs 7. In the embodiment disclosed, the separating discs 7 are conical and extend obliquely downwardly and outwardly from the spindle member 5. The inven- tion is also applicable to rotating members having completely radial separating discs or separating discs which extend in axial planes from the spindle member 5. The rotating member 4 is driven by means of a drive member 8, for instance an electrical motor, and is adapted to bring the gas to rotation in the direction r of rotation for separating, by means of centrifugal forces, liquid impurities from the gas. In the embodiment disclosed, the centrifugal separator also comprises an inlet 9 for the gas to be cleaned, a gas outlet 10 for the cleaned gas, and a first liquid outlet 1 1 for the separated liquid impurities and a second liquid outlet 12 for the separated liquid im- purities. The inlet 9 is provided centrally and extends through the lower end 1 " of the casing 1. The inlet 9 conveys the gas in a central space 15 of the rotating member 4. From this central space, the gas is conveyed radially outwardly to the gaps which are formed between the separating discs 7. The gas outlet 10 is provided at the upper end 1 ' of the casing 1 downstream the rotating member 4.

The first liquid outlet 1 1 is, with respect to the gas flow, provided upstream the gas outlet 10 and downstream the rotating member 4. The second liquid outlet 12 is provided at the lower end 1 " of the casing 1 and, with respect to the gas flow, upstream the first liquid outlet 11. In the embodiment disclosed, the second liquid outlet 12 forms a main outlet, which is adapted for discharge of a main part of the liquid impurities, and the first liquid outlet 11 a residual outlet, which is adapted for discharge of substantially all remaining liquid impurities. The first liquid outlet 11 comprises a number of openings 19, which extend from the separation space 2 through the inner wall surface 3 into a surrounding collecting channel 20. From the collecting channel 20 one or several connection channels 21 extend down to a second surrounding collecting channel 22. The second liquid outlet 12 comprises a number of openings from the lower part of the separation space 2 into the second collecting channel 22. From the second collecting channel 22, the liquid impurities may be conveyed out through a discharge conduit 23. It is to be noted that the sepa- rated liquid impurities may comprise solid particles which are discharged via the liquid outlets 11 and 12.

The centrifugal separator also comprises a disc 30, which is provided between the rotating member 4 and the gas outlet 10. The disc 30 is provided with a number of through-flow openings 31 , in the embodiment disclosed four through-flow openings 31. However, it is to be noted that the disc may comprise more or less such through-flow openings 31 , for instance 2, 3, 5, 6, 7 or more through- flow openings 31. Each through-flow opening 31 comprises a tongue 32, which projects from an edge 31 " of the through-flow opening 31. Each through-flow opening 31 comprises a forward edge 31 ' and a rearward edge 31 " with respect to the direction r of rotation, see Fig. 2. As can be seen in Fig. 1 , each tongue 32 projects from the edge 31 " in such a way that the tongue 32 is located upstream the disc 30, i.e. each tongue 32 has an outer end 33 which is located between the disc 30 and the rotating member 4. Each tongue 32 also has an inner end 34 which coincides with the rearward edge 31 ". Each tongue 32 thus projects from the respective edge 31 " towards the direction r of rotation.

As also can be seen from Fig. 2, each through-flow opening 31 has a substantially arched extension in the direction r of rotation. Also each tongue 32 has a substantially arched extension in the direction r of rotation.

The disc 30 is in the embodiment disclosed substantially planar and parallel with a cross-sectional plane through the centrifugal separator. The axis x of rotation forms the normal to this cross-sectional plane. Each tongue 32 is inclined with an angle α of inclination in relation to the cross-sectional plane. The angle α of inclination may be varied and may be between 1° and 40°.

The gas leaving the gaps between the separating discs 7 thus rotates at a high rotary speed in the direction r of rotation. This rotating movement will continue until the gas reaches the disc 30. The tongues 32 will then function as guide vanes and guide the gas in through the through-flow openings 31. When the gas passes through the through-flow openings 31 , the high rotary speed will be decelerated and converted to an axial flow velocity. In such a way, a large flow of gas may be conveyed axially upwardly to the gas outlet 10. It is to be noted that all gas flowing from the inlet 9 to the gas outlet 10 will be conveyed through the through-flow openings 31 of the disc 30. The gas to be cleaned and conveyed via the inlet 9 into the space 15 will due to the rotation of the rotating member 4 be sucked into the gaps between the separating discs 7. Liquid impurities such as oil will then be attached to these discs 7 and due to the centrifugal force be transported outwardly on the discs 7. Thereafter the liquid impurities leave the discs 7 and are thrown against the inner wall surface 3. The liquid impurities will then flow downwardly on the inner wall surface 3 down to the lower end of the separation space 2 and the second liquid outlet 12 where the liquid impurities may flow to the second surrounding collecting channel 22. A part of the liquid impurities that hit the inner wall surface 3 will due to the gas flow from the rotating member 4 be transported upwardly towards the disc 30 along the inner wall surface 3. These liquid impurities will flow down along the inner wall surface 3 and into the first collecting channel 20 via the openings 19. From the collecting channel 20, the impurities are conveyed via the connect- ing channel 21 down to the second collecting channel 22 from where all separated liquid impurities may be discharged via the discharge conduit 23.

Fig. 4 shows a diagram of the flow Q as a function of the number v of revolutions of the rotating member 4. The diagram shows three curves 41 , 42 and 43. The curves 41-43 disclose the flow measured during experiments made by the applicant. The curve 41 discloses the flow in the case that the centrifugal separator is provided with a disc having through-flow openings 31 but no tongues 32. The curve 42 discloses the flow when the centrifugal separator is provided with through-flow openings 31 and tongues 32 located downstream the disc 30. The curve 43 discloses the flow when the centrifugal separator is provided with a disc 30 with through-flow openings 31 and tongues 32 located upstream the disc 30, i.e. according to this invention. As can be seen, the largest gas flow is achieved with the solution corresponding to this invention.

The invention is not limited to the embodiments disclosed but may be varied and modified within the scope of the following claims.

Claims

1. A centrifugal separator for cleaning of a gas containing liquid impurities, wherein the centrifugal separator comprises - a stationary casing (1 ), which encloses a separation space (2) and has an inner wall surface (3) which faces the separation space, wherein the separation space permits flowing of the gas therethrough,

- an inlet (9) for the gas to be cleaned, - a rotating member (4), which is provided in the separation space (2) downstream the inlet (9) with respect to the gas flow and arranged to rotate in a direction (r) of rotation around an axis (x) of rotation, wherein the rotating member (4) is adapted to bring the gas to rotation in the direction (r) of rotation for separating, by means of centrifugal forces, at least a main part of the liquid impurities from the gas,

- a gas outlet (10), which with respect to the gas flow is provided downstream the rotating member (4) for discharge of the cleaned gas, - at least a liquid outlet (11 , 12) for discharge of the liquid impurities, and

- a disc (30), which is provided between the rotating member (4) and the gas outlet (10) and provided with a number of through-flow openings (31 ) which each comprises a tongue (32) projecting from an edge (31 ") of the through-flow opening (31 ), characterized in that the tongue (32) projects from the edge (31 ") in such a way that the tongue (32) is located upstream the disc (30).

2. A centrifugal separator according to claim 1 , characterized in that the tongues (32) project from the respective (31 ") towards the direction (r) of rotation.

3. A centrifugal separator according anyone of claims 1 and 2, characterized in that the tongues (32) are inclined from the disc (30) towards the rotating member (4).

4. A centrifugal separator according to any one of the preceding claims 1 to 3, characterized in that the through-flow openings (31 ) have a substantially arched extension in the direction (r) of rotation.

5. A centrifugal separator according to any one of the preceding claims, characterized in that the tongues (32) has a substantially arched extension in the direction (r) of rotation.

6. A centrifugal separator according to any one of the preceding claims, characterized in that the disc (30) is substantially planar and parallel with a cross-sectional plane through the centrifugal separator.

7. A centrifugal separator according to claims 3 and 6, characterized in that the tongues are inclined with an angle (x) of inclination in relation to the cross-sectional plane, wherein the angle of inclination is between 1° and 40°.

8. A centrifugal separator according to any one of the preceding claims, characterized in that the disc (30) is arranged in such a way that substantially all gas flowing from the inlet (9) to the gas outlet (10) is conveyed through the through-flow openings (31 ).

9. A centrifugal separator according to any one of the preceding claims, characterized in that the disc (30) comprises at least three such through-flow openings (31) provided with such a respective tongue.

10. A centrifugal separator according to any one of the preceding claims, characterized in that the rotating member (4) comprises a number of separating discs (7).

11. A centrifugal separator according to any one of the preceding claims, characterized in that the centrifugal separator is arranged to be provided in such a way that the axis (x) of rotation extends substantially vertically, wherein the stationary casing (1 ) has an upper end (V) and a lower end (V) and wherein the gas outlet (10) is provided at the upper end (1").