The present invention is an apparatus and process for cleaning substrates using dense fluids under the influence of centrifugal force and dense fluid phase changes. A perforated centrifuge drum operates within a pressure vessel having drains and fill ports. System controls include a high optical sensor, a low optical sensor, a pressure transducer, and a thermocouple. An external dense fluid cleaning and management system exchanges dense fluid and gas with the pressure vessel via the drain and fill ports. Dense fluid centrifugal separations prevent pooling and supercooling of liquid carbon dioxide avoiding recontamination of the substrate. The present invention can perform solvent-aided separation processes including liquid-liquid, liquid-supercritical-fluid, froth flotation and centrifugal phase-shift separations.