Abstract: The present invention relates to an apparatus for separating a fluid flow, the fluid flow comprising lighter and heavier fractions to be separated from each other, the apparatus comprising at least one inlet (22) and at least two outlets (5, 23), the apparatus further comprising a rotary centrifuge device (1), the lighter fractions being carried further on through one of the outlets (23) and the heavier fractions being carried through the other one of the outlets (5). The invention is characterized in that a spin-up assembly (17) is arranged upstream of the rotary centrifuge device (1), the spin-up assembly (17) being configured in such a manner that the fluid flow entering the rotating cylinder (1) is imparted a rotational movement, the rotational velocity of the cylinder (1) being adjustable so that the relative velocity difference between the rotating movement of the fluid flow and the rotational velocity of the centrifuge device (1) is optimal in terms of separation.