Abstract: A separation system for separating oil and water components of a liquid mixture wherein the oil component is comprised of droplets of a less dense phase in a more dense water phase. The mixture is fed to separation devices including a hydrocyclone for generally reducing the oil in water concentration to less than 500 ppm. The underflow of the hydrocyclone is passed to a downstream flotation device for further separation as by settling, which may be further assisted by liberating gas in the mixture, in the flotation device, to adhere such gas to oil droplets and thereby carry such droplets to the surface of the device. Pressure of fluids leaving the hydrocyclone may be reduced before entering the flotation device. A residence vessel upstream of the hydrocyclone may be provided to precoalese the mixture prior to entering the hydrocyclone.

Abstract: A cyclone separator (10) of the dewatering type which comprises an elongated separating chamber (12) having an axis of symmetry between opposite first and second ends, the separating chamber being of greater cross-sectional dimension at the first end than at the second end. The cyclone separator further includes at least one inlet (20) which is adjacent the first end and at least one overflow outlet (25) for the less dense component and at least one underflow outlet (24) for the more dense component (24). The cyclone separator has a first section (14) which contains the feed inlet (20) and the first section is of reduced cross-sectional dimension d.sub.2 at its downstream end relative to the upstream end and is characterized in that the ratio of cross-sectional dimension of the overflow outlet for the less dense component d.sub.0 to the cross-sectional dimension of the first section at its downstream end d.sub.2 is as follows 0.25<D.sub.0 /d.sub.2 0.65.