Imperforate bowl: centrifugal separators – Rotatable bowl – Including discharge-related structure in nature of static...
Patent
1994-03-09
1995-04-11
Scherbel, David A.
Imperforate bowl: centrifugal separators
Rotatable bowl
Including discharge-related structure in nature of static...
494 70, B04B 108, B04B 1108
Patent
active
054053072
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention concerns a centrifugal separator comprising a rotor, which is rotatable around a rotational axis and has an inlet for the liquid to be centrifugally treated and an outlet chamber for a liquid separated in the rotor, the outlet chamber surrounding the rotational axis and being so designed that liquid present in the outlet chamber during operation forms a rotating liquid body around the rotational axis which has a radially inwardly facing free circular liquid surface at a certain radial level in the rotor. The centrifugal separator also comprises: a stationary discharge device in the outlet chamber, extending from the said liquid body radially inwardly to the central outlet, and, in the area of the free liquid surface forming an inlet opening, which is directed towards the rotational direction of the liquid body and is partly located in the liquid body, the discharge device also forming a flow channel, which connects the inlet opening to the central outlet.
BACKGROUND OF THE INVENTION
A centrifugal separator of the kind referred is shown in WO 88/102664. Because the inlet opening of the outlet device in this centrifugal separator during operation is located only partly radially outside the free a liquid surface, a liquid of a high viscosity can be separated in and discharged out of such a centrifugal separator. However, the flow conditions in the flow channel near the inlet opening are such that a part of a liquid of high viscosity flowing into the flow channel turns and flows out again into the outlet chamber through the part of the inlet: opening located radially inside the free liquid surface. This results in a low outlet pressure, a great risk of air admixture and an increased risk of instability.
If one tries to reduce the return flow of separated liquid from the flow channel out through the inlet opening to the outlet chamber by diminishing the radius of the free liquid surface a wave is created in front of the inlet opening, the energy consumption increases to a high degree and the outlet pressure becomes low.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a centrifugal separator of the kind initially described, in which a liquid of viscosity higher than 100 cSt can be separated and discharged out of the outlet chamber with a satisfactory high outlet pressure and low risk of air admixture and instability.
In accordance with the invention the foregoing object is achieved by designing a centrifugal separator of the kind described having an inlet opening, which is delimited by an edge, which upstream of the inlet opening has a front edge portion radially inside the free liquid surface and downstream of the inlet opening has a rear edge portion radially outside the free liquid surface. A straight line drawn through said edge portions forms an angle with a tangent to the free liquid surface at the inlet opening which is greater than 20.degree. but smaller than 50.degree., and the vertex of the angle being directed in the rotational direction.
By designing the inlet opening in this way one causes the part of the separated liquid, which flows out again through the inlet opening, immediately to flow against the free liquid surface, so that it is once again conducted into the flow channel.
In a preferred embodiment of the invention the discharge device has at least one tubular element, which forms a part of the flow channel, and which during operation has its radially outermost part located in the rotating liquid body while the remaining parts of the discharge device are located radially inside the rotating liquid body.
In order to make adjustment of the radial position of the free liquid surface possible if is proposed, in another embodiment of the invention that the tubular element be arranged movably in the discharge device in such a way that the inlet opening of the flow channel can be placed at a variable radius.
The tubular element is then preferably movable along its longitudinal axis.
In a special embodiment of the invention
REFERENCES:
patent: 1256810 (1918-02-01), Leitch et al.
patent: 2622796 (1952-12-01), Steinacker et al.
patent: 2622797 (1952-12-01), Hemfort
patent: 2667338 (1954-01-01), Hemfort
patent: 4406652 (1983-09-01), Nielsen
patent: 5160311 (1992-11-01), Inge et al.
Borgstrom Leonard
Brehmer Patrik
Carlsson Claes-Goran
Franzen Peter
Inge Claes
Alfa Laval Separation AB
Cooley Charles
Scherbel David A.
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