Centrifugal separator with a discharge device

Details Centrifugal separator with a discharge device Centrifugal separator with a discharge device

1990-01-17

1991-06-18

Jenkins, Robert W.

Imperforate bowl: centrifugal separators

Rotatable bowl

Including discharge-related structure in nature of static...

494 68, B04B 1100

Patent

active

050246488

DESCRIPTION:

BRIEF SUMMARY
The present invention concerns a centrifugal separator comprising a rotor, which forms an inlet for a liquid mixture, a separation chamber, connected to the inlet, for separation of components in the liquid mixture and a discharge chamber. The discharge chamber is delimited by two axially separated end walls and a circumferential wall extending between these and which has an inlet connected to the separation chamber, an outlet in a discharge device arranged in the discharged chamber and means, which together with parts of inner surfaces of the discharge chamber are arranged, during operation of the rotor, to entrain into rotation a liquid component present in the discharge chamber so that this forms a rotating liquid body. This liquid body has a radially inwards directed annular free liquid surface radially inside the circumferencial wall. The discharge device extends during operation from a liquid free central part of the discharge chamber to a level radially outside the free liquid surface.
In hitherto known centrifugal separators of this kind said entraining means consists of wings in the discharge chamber, which has an axially and a radially extension. The during operation of the rotor rotating liquid body in the discharge chamber then will be in contact with wings and in contact with the part of the discharge device extending radially outside the level of the free liquid surface of the rotating liquid body. The discharge device, which is stationary or rotates with a lower rotational speed than the rotor, then slows down the rotational movement of the liquid body while the rotating wings entrains the liquid body in the rotational movement of the rotor. Hereby, different parts of the liquid body will obtain different rotational speeds and be influenced by different centrifugal forces. This creates an internal circulation inside the discharge chamber, a liquid formed component flowing radially inwards in layers along the outside of the discharge device and radially outwards in layers along the wings. The flow rate of the component at the free liquid surface and along the wings can then be considerable, which means an increased risk of having air or another gas present radially inside the free liquid surface entrained by the flowing component and to follow it out through the inlet of the discharge device and further out through the outlet. A part of the entrained air then might be dissolved in the separated component while a part is entrained in the form of air bubbles. Besides, entraining means in the form of such wings also creates mechanical strains on the separated component, which in many cases has a damaging influence on the same.
To decrease the admixture of air in the component flowing through the outlet the radial distance between the free liquid surface and the inlet of the discharge device can be increased. A part of the air which has been entrained by the separated component at the liquid surface and which follows it radially outwards towards the inlet of the discharge device is separated in the form of air bubbles, which move radially inwards towards the free liquid surface. The greater the radial distance is between the free liquid surface and the inlet of the discharge device the less admixture of air is obtained in the discharged component.
The problem described above is present especially in centrifugal separators, in which the discharge chamber is open towards the surroundings of the rotor via a gap between the radially innermost edge of the discharge chamber and the discharge device. This edge limits the possibility in these centrifugal separators to increase said distance. In many cases this means that an air free component can not be obtained.
The object of the present invention is to provide a centrifugal separator of the kind initially described, in which a separated component can be discharged out of the discharge chamber having a small degree of air admixture and be entrained gently in the discharge chamber.
This is achieved according to the invention by the fact that said entrain

REFERENCES:
patent: 2302381 (1942-11-01), Scott
patent: 3371858 (1968-03-01), Shapiro
patent: 3494544 (1970-02-01), Thylefors
patent: 4210275 (1980-07-01), Zettier
patent: 4718887 (1988-01-01), Gunn
patent: 4729759 (1988-03-01), Krook

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