Method for separating liquid mixture in centrifugal separator

Abstract

The invention provides a method (100) for separating a liquid mixture into at least a light phase and a heavy phase in a centrifugal separator (1). The centrifugal separator (1) comprises a centrifuge drum (5) and drive means (3) for rotating the centrifuge drum about an axis of rotation (X). The centrifuge drum (5) further comprises an inlet (14) for receiving the liquid mixture, a first outlet (7) for the separated light phase and a second outlet (6) for the separated heavy phase, and wherein the centrifuge drum (5) encloses a separation space (9a) and a sludge space (9b) arranged radially outside the separation space (9a). The centrifuge drum (5) further comprises at least one outlet conduit (30) for conveying the heavy phase from the sludge space (9b) to the second outlet (6). The method (100) comprises the steps of: a) rotating (101) the centrifuge drum (5) at a first speed; b) supplying (102) the liquid mixture to be separated to an inlet (14) of the centrifuge drum (5). The method further comprises a step c) of rotating (103) a component (30, 42) in the sludge space (9b) at a second speed different from the first speed in order to convey a heavy phase from the sludge space (9b) into the at least one outlet conduit (30); and a step d) of discharging (104) the separated light phase from said first outlet (7) and discharging (104) the separated heavy phase from said second outlet (6). Steps c and a) are performed simultaneously such that the components (30, 42) in the sludge space (9b) rotate at a differential speed compared to the centrifuge drum (5).

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