A centrifugal separator for separation of particles from a gas stream is disclosed. The centrifugal separator includes a self-supporting frame for mounting inside an existing vessel for guiding the gas stream. The frame comprises a holder configured to hold the frame at a position inside the vessel, and a first partition for dividing the vessel into a first section and a second section. The first section is upstream of the second section. The separator includes a gas inlet communicating with the first section, and a gas outlet communicating with the second section. A centrifugal rotor is arranged to be rotatably supported in the frame around a rotational axis, the rotor having a first and a second end portion and including a plurality of separation plates defining separation passages between the plates. The centrifugal separator is configured such that the first and second sections communicate via the separation passages of the rotor.