Spirals are sorting devices which separate the materials according to their different densities. They can be used for a grain size range from approx. 0.04 mm to 4 mm, with a throughput per spiral of approx. 1–4 t/h. If a higher throughput is required, 2 or 3 spirals can be combined to form one column. Several spiral columns can be joined to form banks of 2, 4, 6 or 8 with one distributor for the inlets and collector chutes for the outlets. Different types of spirals for heavy, middling and light density products.
Principle of operation
The slurry (content 10 – 40% solids depending on application) is fed into the spiral from the top. Spread on the spiral bottom, it moves down by gravity. A transverse flow is directed inwards on the sluice bottom or outside on the slurry surface is superimposed on the main flow. This combination results in a separation of the particles contained in the suspension, depending on their density. Particles with a lower specific gravity, such as wood, coal or organic matter, are concentrated in the outer areas of the flow. Particles with a higher specific gravity are transported towards the spiral axis.
Design features and advantages
Separation of lightweight fraction by force of gravity
Separation of heavy minerals from quartz sands
Separation of up to 3 fractions: heavy, middling and light density products