Hydrocyclones

Hydrocyclones are devices used to separate and classify particles in a liquid suspension by applying centrifugal forces. They consist of a cylindrical section attached to a conical section, with a tangential feed inlet, an overflow outlet at the top, and an underflow outlet at the apex. The slurry enters tangentially, creating a high-speed, swirling flow. Denser and coarser particles are driven outward toward the wall and downward to the underflow, while lighter particles and clarified liquid move upward and exit through the overflow. The separation efficiency depends on particle density and size, liquid viscosity, solids concentration, and the operating pressure or feed velocity.

Hydrocyclones have no moving parts and are valued for their simple, compact, and robust design, enabling continuous operation in a wide range of processes. They are commonly used as separators or classifiers in mineral processing, coal preparation, industrial wastewater and slurry treatment, and pulp and paper operations. In some circuits, desliming or desanding cyclones remove fines or fines from a stream prior to downstream processing, while multi-stage cyclone banks enable progressive size separation or enhanced recovery.

Key design and operating parameters include cone angle, geometry of the apex and overflow outlets, feed pressure, solids loading, and the presence of a vortex finder. Common limitations include wear of linings, reduced efficiency for very fine or very close-density particles, sensitivity to slurry rheology, entrainment of fines in the underflow, and energy requirements to maintain the necessary flow. Properly selected and operated hydrocyclones can provide high throughputs with relatively low maintenance for continuous separation tasks.