How do spiral concentrators work?

Although they’re widely used in our industry for separation, spiral concentrators may still carry an element of mystery to some. That’s why we’ve decided to share the ABCs of spiral concentrators.

The spiral concentrator is a modern device that features high capacity at a low cost. It’s designed to concentrate low-grade ore and industrial mineral slurries, using a combination of solid particle density and hydrodynamic dragging. Two or more spirals are built around one main central column, thus increasing the amount of material that can be processed by a single unit.

Spiral concentrators are gravity-based and used to separate low-density granular and sandy (from 18 mesh to 200 mesh—1 mm to 0.0757 μm) materials from higher-density materials.

Spiral concentrators are used in many mineral processing applications. For instance, they’re used to process heavy mineral sand deposits, more specifically deposits containing minerals such as zircon, monazite, and rutile.

Obtaining good separation

In order to obtain good separation, there should be at least 1.0 SG of difference (mainly ranging from 20–40% solids). This range should provide maximum efficiency, depending on the characteristics of the mineral being processed. The only equipment required is typically some slurry pumps for the slurry to be separated, and then the banks of spirals with a feed distributor.

How exactly do they work?

Slurry is pumped to the upper part of the spiral, which is usually 33 to 38 cm from the floor. From there, it enters a feed distributor, which evenly distributes the feed to each spiral concentrator. Gravity, along with the specific design and shape of the spiral, are the key to making it work. Materials are separated through stratification, thanks to centrifugal force, differential settling and the migration of heavy particles through the bed and into the inner part of the conduit. As the slurry makes its way down the spiral, the mineral particles settle. They’re sorted mostly according to their size and density, but also partially to their shape. The lower-density particles are carried with the bulk of the water to the outside of the spiral (called the “perimeter”), while higher-density particles travel towards the inside of the spiral.

Applications of spiral concentrators

Spiral concentrators are used for a number of mineral processing applications. They’re extensively used to process heavy mineral sand deposits, including monazite, zircon, ilmenite and rutile deposits. More recently, spiral concentrators have been widely used to recover fine coal as well as gold, iron ore and other minerals.

The importance of finding the right spiral for your application

For every separation process, there is a spiral concentrator that’s specifically adapted to meet your needs. That’s Multotec’s specialty.

Spirals for heavy ores

For the separation of fine heavy minerals, Multotec’s ranges of mineral spiral concentrators greatly facilitate the processing of 1.5 o;mm to 0.1 mm particles. They’re ideal for iron ore, chrome, mineral sands and high-density ores.

Their modular frames house two spiral assemblies (offered in the HX3, HX5 and SC ranges) and have a number of optional features. They can also be fully dismantled for retrofitting. Parts include a spiral trough, auxiliary or sliding splitters, launders, distributors and piping, a feed box and a product box with product splitters. Each of these boasts features that provide longer life, increased production, ease of repair and marked advantage of reduced downtime.

Coal spirals

Multotec’s coal spirals come in both single (SX4) and double (SX7 and MX7) stage formats that are optimised to be compatible with coal concentrators. The coal spirals can be assembled in single, double or triple starts with up to seven turns high or low feed ash profiles to suit your needs. Developed for coarse coals, they’re guaranteed to make your separation even more efficient.

Proven results

New research and development have shown that our compact, modular designs add flexibility when building or replacing spiral plants, with the distinct advantage of extending the life of your plant while reducing overall maintenance costs.

Dedicated to serving your specific needs

Multotec spiral concentrators are used throughout the world in plants that process materials like coal, gold, iron ore, mineral sands, platinum and chrome.

Our turnkey equipment for gravity concentration is used around the world because the Multotec team can deliver end-to-end spiral solutions, ranging from process audits and test work to complete spiral concentration plants that are optimized for your processes. Our global branch network supports you with tailored field service, readily available spare parts and our signature after-sales service.

Learn more about our product range, which includes spiral banks, slurry distributors and pipe launders.