WO1986006006A1

WO1986006006A1 - Centrifugal separator comprising a rotor, which around its circumference has outlets for intermittently discharging a separated product and outlet for discharging an operating liquid

Info

Publication number: WO1986006006A1
Application number: PCT/SE1986/000156
Authority: WO
Inventors: Klaus Stroucken
Original assignee: Alfa-Laval Separation Ab
Priority date: 1985-04-11
Filing date: 1986-04-04
Publication date: 1986-10-23
Also published as: SE447544B; EP0220229A1; SE8501781D0; CN86102095A; SE8501781L; JPS62502454A; JPH0622702B2; KR870700410A

Abstract

Centrifugal separator comprising a rotor (1), which around its circumference during operation has openable first outlets (4) for intermittently discharging a separated product and second outlets located axially at a distance from these outlets (4) for discharging an operating liquid, which is supplied to the rotor for operating the first outlets (4); the centrifugal separator also comprising a casing (3) around the rotor (1) and means arranged to form a first chamber (12) around the rotor inside the casing for receiving and leading away a separated product coming out of the first outlets (4) and a second chamber (13) around the rotor for receiving and leading away an operating liquid coming out of the second outlets (5). To eliminate the risk for the separated product and the operating liquid to be mixed up with each other caused by entraining air flows between the two chambers (12 and 13), according to the invention these are separated from each other by means of two separating walls (10 and 11), arranged at an axial distance from each other and extending around and close to the rotor (1) and between themselves delimiting an intermediate chamber (14), which is open towards the rotor (1) and communicates with the atmosphere outside the casing (3).

Description

Centrifugal separator comprising a rotor, which around its circumference has outletB for intermittently discharging a separated product and outlet for discharging an operating liquid

The present invention relates to centrifugal separators of the kind, that comprises a rotor, which around its circumference during operation has openable first outlets for intermittent discharge of a separated product and second outlets located at a distance axially from these ones for discharge of an operating liquid, which has been supplied to the rotor for operating the first outlets, the centrifugal separator also comprising a casing around the rotor and means arranged to form a first chamber around the rotor inside the casing to receive and to lead away a separated product coming out of the first outlets and a second chamber around the rotor to receive and to lead away the operating liquid coming out of the second outlets.

In a previously known centrifugal separator of the kind that has a rotor which is supported by a vertical shaft, the two chambers inside the casing around the rotor are separated by an annular separating wall. This separating wall is formed by the casing itself and is formed like an upwards open groove around the rotor in said first chamber for the guidance of the received product towards an outlet. The second chamber has a separate outlet for the received operating liquid. The two chambers communicate with each other via a gap between the rotor and the separating wall and to the surrounding of the casing via their respective outlets, the chamber for the operating liquid .also being in communication with the surroundings of the casing via a not sealed opening in the bottom of the casing, through which the driving shaft extends.

During operation of such a known centrifgal separator the air around the centrifuge rotor is brought into rotation by its friction against the outside of the rotor. Hereby a pupmp-like effect is created, which occurs in the two chambers. As a consequence of different designs of the chambers and the outlets connected thereto in these centrifugal separators the effect is obtained that air flows into the second chamber partly through the outlet for the operating liquid, from there further via the gap between the rotor and the separating wall to the first chamber and out through the outlet for the separated product. Air can also flow into the second chamber through the above mentioned opening in the bottom of the casing, there being a risk that oil from bearings located underneath is entrained by the air flow into the two chambers.

The air flow created in this manner by the rotation of the rotor causes that a part of the operating liquid, which continuously or intermittently leaves the rotor, is entrained via said gap into the receiving chamber for the separated product.

Upon opening of the outlet of the rotor for the separated product said air flow is influenced by the flow of the product out of the rotor. Generally, the pressure in the first chamber is then increased in such degree that an air flow in the opposite direction is created through the gap between the rotor and the casing. Such a reversed air flow results in a part of the discharged separated product being entrained into the receiving chamber for the operating liquid.

The above described air flows and the accompanying transport of operating liquid and separated product, respectively, cause several disadvantages. Thus, it is normally not desirable that operating liquid is lost into the separated product and/or that the concentration of the latter decreases. Even by other reasons it is often unacceptable that the separated product is mixed up with the operating liquid. It is further not desirable that separated product flows into the receiving chamber for the operating liquid because partly it pollutes the operating liquid and partly there is a risk that the separated product might be soaked into the operating system of the rotor and cause a stand¬ still.

The object of the present invention is to remove the above mentioned disadvantages in previously known centrifugal separators of the kind stated in the introductory part of the specification and to provide an effective screening between the separated product and the operating liquid, in such a way that they will not be mixed up with each other. According to the invention this is achieved by the fact that said two chambers are separated by means of two separating walls arranged at an axial distance from each other and extending around and close to the rotor and between themselves defining an intermediate chamber, which is open towards the rotor and communicates with the atmosphere outside the casing.

In the following the invention will be described more in detail with reference to the accompanying drawing. In this a part of a centrifugal separator according to the invention is shown partly in a side view and partly in section.

The centrifugal separator shown in the drawing has a rotor 1, which is driven and supported by a vertical shaft 2 and is surrounded by a stationary casing 3. Around its periphery the rotor is provided with a number of first outlets 4, through which a product separated in the rotor can be discharged intermittently. At an axial distance from these the rotor 1 is provided with at least one second outlet 5 for discharging an operating liquid, which is supplied to the rotor for operating the first outlets 4. The shown rotor is also provided with a central inlet 6 for a liquid mixture, which is to be centrifugally treated, and two central outlets 7 and 8 for two liquid components separated in the rotor. The casing surrounding the rotor is supported by a frame 9 and is designed with two separating walls 10 and 11, which at an axial distance from each other extend around and close to the rotor. The space between the rotor 1 and the casing 3 is hereby divided into three chambers around the rotor, a first chamber 12, intended to receive and to lead away separated product coming out of the outlets 4, a second chamber 13 intended to receive and to lead away operating liquid, which flows out of the second outlet 5 and an intermediate chamber 14 delimited by the two chambers 12, 13. The upper separating wall 10 is formed like a groove 15 around the rotor in the chamber 12 for the guidance of received separated product towards an outlet 16. In order to guarantee the collection and conduction away of the separated product, the groove 15 is located at a lower level than the part of the separating wall 10, which is located closest to the rotor.

The second chamber 13 is also provided with an outlet 17, through which operating liquid is to be conducted out of this chamber. The chambers 12 and 13 communicate with the atmosphere surrounding the casing via the respective outlet 16, 17.

In the shown embodiment the intermediate chamber 14 communicates with the atmosphere surrounding the centrifugal separator via a passage 18 in the frame 9.

By designing a centrifugal separator in the described manner air flows are avoided between the receiving chamber 12 for the separated product and the receiving chamber 13 for the operating liquid. Unavoidable air flows in direction from these two cham¬ bers are instead conducted via the intermediate chamber 14 out through the passage 18, since its respective flow paths offer the lowest flow resistance. Thus, the product and the operating liquid, respectively, which eventually are entrained by such air flows accordingly leave via the passage 18. An effective scree- ning between the two spaces 12 and 13 will hereby be obtained, and there is no longer any risk that the separated product and the operating liquid will be mixed up and pollute each other.

The pressure in the above-mentioned and in the following claims mentioned atmosphere, to which the intermediate chamber 14 is connected via the passage 18, is normally atmospheric pressure, but the passage 18 can also be connected to another pressure.

Claims

1. Centrifugal separator comprising a rotor (1), which around its circumference during operation has openable first outlets (4) for intermittently discharging a separated product and a second outlet (5) located axially at a distance from these outlets (4) for discharging an operating liquid, which has been supplied to the rotor (1) for operating the first outlet (4); the centrifugal separator also comprising a casing surrounding the rotor (1) and means arranged inside the casing to form a first chamber (12) around the rotor to receive and to lead away a separated product coming out of the first outlets (4), and a second chamber (13) around the rotor to receive and to lead away the operating liquid coming out of the second outlet (5), c h a r a c t e r i z e d i n that said two chambers (12 and 13) are separated by two separating walls (10 and 11) arranged at an axial distance from each other, and extending around and close to the rotor (1) and between themselves delimiting an intermediate chamber (14), which is open towards the rotor (1) and communicates with the atmosphere outside the casing (3).

2. Centrifugal separator according to claim 1, c h a r a c ¬ t e r i z e d i n that the delimiting walls of said ^' intermediate chamber has essentially the form of an annular groove (15) which is open towards the rotor (1).

3. Centrifugal separator according to any of the previous claims, c h a r a c t e r i z e d i n that at least one of the separating walls is formed by the casing (3).

4. Centrifugal separator according to any of the previous claims, c h a r a c t e r i z e d i n that an annular portion of at least one of the separating vails located closest to the rotor extends in a direction towards the rotor (1).

5. Centrifugal separator according to any of the previous claims, at which the rotor (1) is supported by a vertical driving shaft (2), c h a r a c t e r i z e d i n that the upper separating wall (10) in said first chamber (12) forme an annular groove (15) around the rotor, which groove is located at a lower level than the portion of the separating wall (10), which is located closest to the rotor (1).

6. Centrifugal separator according to any of the previous claims, c h a r a c t e r! z e d i n that every one of said chambers (12 and 13) and the intermediate chamber (14) are annular designed.