Abstract: A hydrocyclonic apparatus has been designed to separate a less dense dispersed phase (either liquid or solid) from a more dense liquid phase. The cyclone separator consists of two generally cylindrical portions positioned around the longitudinal axis in a `piggyback` manner. A vortex finder with an orifice plate captures the dispersed particles entrained in a local secondary flow established by the unique operating and design parameters of the device. Clear fluid is removed from the apparatus through an underflow tube opposite the vortex finder tube. The liquid feed containing dispersed particles is introduced into the primary cyclone around the vortex finder as a swirling annular jet. Another stream, containing no dispersed phase, is introduced as a tangential flow surrounding the annular jet. A polymer stream is injected into the core of the vortex flow of the primary cyclone to increase the stability of the vortex core and to moderate the turbulence.