Method and system for purifying contaminated oil

A method for purifying an oil containing contaminants, the method comprising:

• i. introducing a mixture of the oil and a separation aid through a hermetic inlet of a centrifugal separator and into a separation chamber of a rotating separator bowl of the centrifugal separator, the hermetic inlet sealing off an inlet port of the centrifugal separator so that no atmospheric gases are introduced and mixed into the mixture via the input port while the mixture is being fed from a fluid conduit into the centrifugal separator, the separation aid having a density higher than the density of the oil,
• ii. separating the separation aid and contaminants absorbed and/or adsorbed in the separation aid from the oil in the separation chamber,
• iii. discharging oil from a light phase outlet of the separation chamber, and
• iv. discharging separation aid having contaminants absorbed and/or adsorbed therein from a heavy phase outlet of the separation chamber,
• wherein the separation aid:
• is a liquid at the temperature at which the method is being performed,
• is polar and at least substantially insoluble in the oil, thereby forming a two-phase mixture with the oil upon mixing with the oil, and
• chemical interacts with contaminants in the oil and thereby adsorbs and/or absorbs contaminants in the oil.