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Choosing gravity separation equipment starts with the material entering the machine. Mineral density matters, but so do liberation, particle size, feed rate and the required concentrate quality.
A centrifugal concentrator, shaking table and spiral concentrator can all recover heavy minerals. However, they perform different duties and should not be selected by nominal capacity alone.
This guide compares these three common equipment types and explains how to match them to a mineral processing application.
Gravity separation uses differences in particle behavior under gravity or enhanced gravitational forces. Density is important, but particle size and shape also influence separation.
The valuable mineral must be sufficiently liberated for its properties to differ from those of the unwanted material. A dense mineral locked inside a lighter particle may not respond like a liberated grain.
Before comparing equipment, establish:
A high feed grade does not automatically indicate good gravity response. Representative separation tests provide a stronger basis for selection.
| Equipment | Common Duty | Main Selection Considerations |
|---|---|---|
| Centrifugal concentrator | Recovery of liberated dense minerals, particularly free gold in suitable applications | Gravity response, feed size, water requirements and concentrate discharge mode |
| Shaking table | Separation of classified feed or upgrading of gravity concentrates | Particle-size distribution, solids loading, wash water and required product quality |
| Spiral concentrator | Continuous concentration of suitable mineral slurries | Mineral density, feed grading, slurry flow, solids concentration and feed distribution |
These are typical duties rather than fixed rules. Equipment design and test results determine the operating limits of a particular application.
A centrifugal concentrator uses a rotating bowl to create an enhanced gravitational field. It can be considered where liberated dense particles are difficult to recover using conventional gravity equipment.
Free-gold recovery is a common application. However, a centrifugal concentrator cannot compensate for gold that remains enclosed in other minerals.
Important selection questions include:
Discharge mode matters when integrating the machine into a plant. Concentrate collection and subsequent treatment must suit the actual operating cycle.
A shaking table combines deck motion and flowing water to separate particles into different product streams.
Tables can treat suitably prepared ore or upgrade an existing gravity concentrate. Applications include gold, tin, tungsten and tantalum-bearing materials, where mineral characteristics support separation.
Feed preparation is especially important. A broad mixture of coarse and fine particles can make separation more difficult, while unstable feeding can disturb the product bands.
Evaluate the table using the stream it will actually receive. A table cleaning a small concentrate stream should be sized for that duty rather than the plant’s total ore throughput.
Where middlings are produced, testing should establish whether they need further cleaning, regrinding or another treatment.
A spiral concentrator separates particles as slurry flows down a shaped spiral trough. Separation depends on density, size, shape and the flow conditions within the trough.
Spirals are used in applications such as chromite, iron ore and mineral sands processing. They can perform roughing, cleaning or scavenging duties, depending on the circuit.
The spiral trough has no moving parts, but the complete system still needs suitable slurry delivery and feed distribution.
For selection, check:
Do not apply one universal particle-size range to every spiral. Different trough designs serve different materials and separation duties.
Gravity equipment responds to particle size as well as density. Preparing a suitable size range can therefore improve the conditions for separation.
Classification may divide the feed into streams for separate treatment. Screening may remove material that exceeds an equipment feed limit.
Desliming requires more care. Removing fine material may improve downstream operation, but the removed stream can also contain valuable minerals.
Before discarding slimes, measure their mass and valuable-mineral content. Feed preparation should improve the complete circuit’s performance rather than transfer losses to an unexamined stream.
Yes. Different machines can perform successive duties when testwork supports the arrangement.
For example, a centrifugal concentrator may recover a gravity concentrate that is subsequently cleaned on a shaking table:
Prepared Feed → Centrifugal Concentration → Concentrate Cleaning → Upgraded Concentrate
The centrifugal tailings form a separate stream. Their destination must be determined by the overall flowsheet rather than assumed to be final waste.
A spiral circuit may similarly use rougher and cleaner stages. Middlings may require further treatment, but returning them indefinitely can increase circulating load.
A complete flowsheet should identify the destination of every concentrate, middlings and tailings stream.
Compare equipment using the same feed and separation objective.
Record dry solids throughput and slurry flow separately. Two feeds with the same tonnes per hour can impose different hydraulic loads if their solids concentrations differ.
Test results should report more than recovery alone:
| Result | Why It Matters |
|---|---|
| Concentrate grade | Indicates the quality achieved |
| Recovery | Measures valuable material reporting to the selected product |
| Concentrate mass yield | Establishes the load sent to downstream treatment |
| Performance by size fraction | Identifies where recovery or selectivity changes |
| Water requirements | Supports utility and operating-cost assessment |
| Response to feed variation | Helps evaluate operation beyond one test condition |
A higher recovery obtained by collecting much more gangue may increase downstream processing requirements. Compare grade, recovery and mass yield together.
Prepare the mineral type, available mineralogical information, feed-size distribution, required throughput and representative test results.
Also provide the proposed equipment duty, water availability and target product quality. Explain whether the machine will treat original feed, a classified fraction, a concentrate or a tailings stream.
LIPU supplies centrifugal concentrators, shaking tables and spiral concentrators. Share your material information and processing requirements to discuss suitable equipment and testing needs.
Which gravity separator is best for gold recovery?
The choice depends on how the gold occurs and the prepared feed. A centrifugal concentrator may be evaluated for liberated gold recovery, while a shaking table may treat classified feed or clean gravity concentrates. Testwork should establish the appropriate duties.
Can a shaking table process raw ore directly?
It can treat suitably prepared ore within its operating limits. Unscreened feed containing oversized particles, clay lumps or excessive slimes may require preparation before tabling.
Is a spiral concentrator only used for gold?
No. Spirals are used for several mineral applications, including chromite, iron ore and mineral sands. Suitability depends on the material and spiral design.
Should all fine material be removed before gravity separation?
No. Fine fractions may contain recoverable valuable minerals. Assess their mass, grade and separation response before deciding whether to remove or treat them separately.
Can gravity separation replace flotation or other processes?
In some applications it can provide the main separation stage. In others, it forms part of a combined flowsheet. The decision depends on liberation, process response and the required final product.
We provide a variety of mining and processing equipment, including feeders, rock crushers, grinders, classifying and screening machines, washing machines, gravity separators, flotation machines, magnetic separators, electric separators, dewatering equipment and laboratory mineral processing equipment.
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