Spiral Concentrator

We’ll help you lower your cost per ton targets

Our process engineers will work with you to optimise your spiral concentrator plant, taking into consideration the feed grade, targeted product grade, recoveries and mass yields.

Whether for a greenfield plant, or optimisation or refurbishment of an existing plant, Multotec has the technologies and expertise to help you ensure maximum gravity separation efficiency.

Spiral Separation services

Your local Multotec branch will help you with end-to-end solutions for your gravity concentration plant, from testing equipment through to field services, ongoing optimisation and any maintenance. We keep a wide range of spares and accessories for your spirals, reducing lead times to ensure maximum processing uptime.

Our gravity separation services include:

• Test work on spiral concentrators
• Consultation on spirals, processes and your plant
• Commissioning of all spiral equipment
• Ongoing optimisation
• Design assistance

Read more about Multotec field service offerings.

Spiral Separators for heavy minerals

Our gravity separators for heavy mineral applications, including iron ore, chrome, mineral sands and other high density minerals, separate particles in the size range 2 to 0.04 mm.

We have a range of spirals, from 3 to 12 turns, with high-, medium- and low-gradient profiles. Our high capacity spirals (the HX series) provide a per-start tonnage rating of 4 to 7.5 tons per hour, depending on the mineral type, and is especially suited for the treatment of low-grade ore, where large tonnages are processed.

Mineral spiral separator components include the spiral trough; sliding or auxiliary splitters; launders; distributor and piping; feed box; product box and stainless steel product splitters; and the discharge chute at the bottom of the modular housing frame. Our spiral separators have a diameter of +/- 950 mm.

Gravity Separators for coal

Our single- and double-stage spiral separators are optimised for coal particles in the size range of 1 to 0.1 mm, providing enhanced coal washing for slurries. Their compact, modular design provides flexibility when building or upgrading your plant.

Double start spirals reduce the requirements of height and floor space in a plant, and reduce capital and operating costs. The MX7 spiral separator is ideal for difficult-to-wash coals, improving the overall efficiency of tougher separation applications.

These gravity concentrators are precisely designed and built from high-quality materials that provide a long service life, lower costs of operation and low maintenance.

The science behind the spiral

Spiral concentrators are simple low energy-consuming devices used for mineral separation mainly on the basis of density or shape. Spirals are widely used in mineral processing as a method for pre-concentration and have proven to be metallurgically efficient and cost-effective.

As the mineral stream is fed from the top of the spiral, a combination of forces act on particles as they move down the trough of the spiral circuit. These forces include gravitational, centrifugal, lift and friction forces, and hydrodynamic drag. Apart from the forces acting on a spiral, the properties of the slurry flowing on a spiral including, solids concentration, feed rate and wash water also plays an important role in mineral separation.

During separation, the heavy particles migrate toward the inner region of the trough, with lighter-density particles migrating to the outer edge of the trough. In a dry spiral separation, materials are sorted by shape. Rounder particles travel faster, are forced to the perimeter of the spiral, from where they can be collected separately from non-round material. 

With over 45 years’ experience in mineral processing applications across the world, Multotec is a leading supplier of gravity concentration solutions that optimise your plant performance.

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 is 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 330 mm to 380 mm 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 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 SC25 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 optimised for your processes. Our global branch network supports you with tailored field service, readily available spare parts and our signature after-sales service.

Frequently asked questions:

What is a spiral concentrator?

A spiral concentrator is a device that relies on gravity to separate material in a slurry feed. The light density granules are separated from the heavier density material.

Why spiral concentrators are used?

Spiral concentrators are low-cost devices, used in mineral processing to process heavy mineral sand deposits, usually containing minerals such as rutile zircon and monazite.

Our gravity separators for heavy mineral applications, including iron ore, chrome, mineral sands and other high density minerals, separate particles in the size range 2 to 0.04 mm.

We have a range of spirals, from 3 to 12 turns, with high-, medium- and low-gradient profiles. Our high capacity spirals (the HX series) provide a per-start tonnage rating of 4 to 7.5 tons per hour, depending on the mineral type, and is especially suited for the treatment of low-grade ore, where large tonnages are processed.

Mineral spiral separator components include the spiral trough; sliding or auxiliary splitters; launders; distributor and piping; feed box; product box and stainless steel product splitters; and the discharge chute at the bottom of the modular housing frame. Our spiral separators have a diameter of +/- 950 mm.