Method and a device for cleaning of a centrifugal separator

A device for cleaning of a centrifugal separator intended for a process of dividing a liquid mixture containing solid particles into a liquid phase, which is substantially free of solid particles and has a relatively low viscosity, and a concentrate phase, which is rich in solid particles and has a relatively high viscosity, which centrifugal separator comprises a rotor (1, 2), which is rotatable around a central rotational axis (4) and which has an inlet (11) for said mixture, an outlet (32) for said liquid phase and an outlet (12) for said concentrate phase, and in which centrifugal separator

• the rotor delimits a process liquid space including at least one separation chamber (5), which has a liquid space (6) for separated liquid phase and a concentrate space (7) for separated concentrate phase, a liquid outlet chamber (28), which communicates with said liquid space (16), and a concentrate outlet chamber (17), which through several concentrate passages (19, 21, 23) distributed around the rotational axis (4) of the rotor communicates with said concentrate space (7),
• each of said concentrate passages (19, 21, 23) extends through a vortex device (20), which is adapted at an unchanged pressure drop across itself to admit a larger through flow of concentrate phase having a relatively high viscosity than of concentrate phase having a relatively low viscosity,
• several vortex devices (20) are distributed around the rotational axis (4) of the rotor, each concentrate passage (19, 21, 23) opening tangentially into a vortex device,
• a liquid outlet member (30), which is adapted not to rotate together with the rotor (1, 2), extends into the liquid outlet chamber (28) for discharge of separated liquid phase,.
• a concentrate outlet member (12), which is adapted not to rotate together with the rotor (1, 2), extends into the concentrate outlet chamber (17) for discharge of separated concentrate phase, and
• means are arranged during normal operation of the centrifugal separator to maintain process liquid, at predetermined radial levels in said process liquid space,
• wherein
• a transferring member (16) delimits at least one separate cleaning liquid passage (34), which connects the concentrate outlet chamber (17) with the separation chamber through a different way than through the liquid outlet chamber (28) and which extends at least partly at a level (C) radially inside that at which process liquid is present, so that no flow of process liquid will occur through the cleaning liquid passage (34) during normal operation of the centrifugal separator, and
• the rotor has limiting walls (31), which are formed in a way such that when a part of the rotor process liquid space other than said concentrate outlet chamber (17) is charged with cleaning liquid this other part is admitted to contain cleaning liquid even radially inside one of said predetermined radial levels, at which process liquid is present therein during normal operation of the centrifugal separator, so that an outflow of cleaning liquid is allowed to come up through the cleaning liquid passage (34) into the concentrate outlet chamber (17).