A centrifugal separator (1) for separation of particles from a gas stream is disclosed, comprising a self-supporting frame (2) for mounting inside an existing vessel (19) for guiding the gas stream. The frame comprises a holding means (20) to hold the frame at a position inside the vessel, and a first partition (15) for dividing the vessel into a first section upstream of the partition and a second section downstream of the partition. The separator comprises a gas inlet (3) communicating with the first section, and a gas outlet (4) communicating with the second section. A centrifugal rotor (5) is arranged to be rotatably supported in the frame around a rotational axis (x), the rotor having a first and a second end portion and comprising a plurality of separation plates (6) defining separation passages (7) between the plates. The centrifugal separator is configured such that the first and second sections communicate via the separation passages of the rotor.
