"Hydrocyclone" is a family name, not a single design. Changing the cone angle, diameter, or the fluid inside changes what the unit actually separates. The four families below cover the great majority of units in mineral processing plants.
Classifying cyclone
Small-diameter / HP
Water-only cyclone
Dense-medium cyclone
4.1 Conventional classifying cyclones
The general-purpose workhorse, typically run with a cone angle around 20°, used to close grinding circuits by returning oversize material to the mill while sending correctly-sized product forward. This is the type most people picture when they hear "hydrocyclone," and everything covered in Lessons 1–3 describes this family directly.
4.2 Small-diameter (high-pressure) cyclones
Shrinking the vessel diameter increases rotational velocity for a given flow rate, which pushes the achievable cut point much finer — down into the tens of microns. A single small unit has limited capacity, so these are almost always run in large parallel clusters (see 4.5) to handle plant-scale tonnage. Common in regrind circuits ahead of flotation, where a very fine, sharp separation matters more than throughput per unit.
4.3 Water-only cyclones
Built with a much wider, shorter cone than a classifying cyclone, water-only cyclones separate primarily by density rather than purely by size, exploiting the difference between a particle's effective settling behaviour in the swirling flow. Widely used in coal preparation to reject dense mineral matter from lighter coal particles without adding any separating medium — just water.
4.4 Dense-medium cyclones (DMCs)
Instead of plain water, the carrier fluid is a suspension of fine, dense particles — most often ferrosilicon or magnetite — engineered to a specific effective density. Ore or coal fed into this medium separates cleanly by density: material lighter than the medium floats to overflow, material denser sinks to underflow, largely independent of particle size. This makes DMCs the standard tool for coarse density-based beneficiation, notably in coal washing and diamond recovery, where they can make a sharp density cut on particles far coarser than a classifying cyclone could size-separate usefully.
4.5 Multi-cyclone clusters
Because a single cyclone has a capacity ceiling set by its diameter, plants scale up by running many identical units in parallel, all fed from a common pressurised manifold and discharging into shared overflow and underflow launders. Clusters can range from a handful of large-diameter units to banks of fifty or more small-diameter units, and let a plant hold a fine cut point while still processing full-scale tonnage.
| Type | Primary basis | Typical duty |
|---|---|---|
| Classifying cyclone | Particle size | Closing grinding circuits |
| Small-diameter / HP | Particle size (fine) | Regrind, flotation feed prep |
| Water-only cyclone | Density | Coal preparation |
| Dense-medium cyclone | Density (medium-assisted) | Coal washing, diamond recovery |
- Cone angle and diameter are the main levers that turn the same basic double-vortex principle into different tools — from fine size classification to coarse density separation.
- Water-only and dense-medium cyclones separate primarily by density rather than size, and are the backbone of coal and dense-mineral beneficiation.
- Fine classification duties are met not with one giant cyclone but with clusters of many small-diameter units running in parallel.