What are the benefits and drawbacks of using gravity separation in mineral concentration methods?

Small-Scale (Limited Resources) Pans/Tube: Inexpensive and manually operated, they allow the separation of heavier particles by tilting, rotating, and gently shaking the pan. The backbone of this operation is that it is suitable for minimal resources. Small-Scale Shaking Tables or Jigs: Affordable, mechanical devices that use shaking and vibrations to separate that can be fabricated easily, requiring minimal infrastructure but feasible for limited resource setups. Large-Scale Centrifugal Concentrators and Dense Media Separators: Mechanized and efficient, these are suitable for large-scale operations as they need more resources and initial investment, with high-capacity gravity separation.

Gravity separation is a relatively simple process, based on SG differences between valuable and gangue minerals. Most technologies are water based, with some dry applications as well. Generally these processes are low energy consumers and for coarser particles >0.5 mm, high capacity. Fine particles separation is also possible down <45 microns. Process control is generally straightforward.

Small-Scale (Limited Resources) - Low Cost: Manual methods like panning are economically viable - Environmentally Friendly: No need for chemicals, minimizing environmental impact - Versatility: Suitable for various ores or (alluvial) without complex equipment Small-Scale - Cost-Effective: Mechanized methods (e.g., shaking tables) are budget-friendly, self-fabricated - Minimal Infrastructure: Requires less complex setup Large-Scale - Operational Efficiency: Scalable for efficient separation in specific large-scale alluvial operations - Reduced Environmental Impact: Minimal chemical usage promotes eco-friendly practices - Resource Recovery: Efficiently recovers particles, maximizing mineral value

As a rule of thumb you need a SG differential of at least 1 for effective gravity separation. Liberation of valuable minerals is critical. The degree of liberation establishes the required SG differential. Near density particles are the curse of gravity separation. This happens when you have ineffective liberation, resulting in the production of composite particles which have a SG close to that of the valuable minerals. This impacts concentrate grade. Fine particles recovery is a major issue. Technologies are available but there will be a sacrifice in capacity.

Particle size- keep a narrow PSD and remove fines for disposal or separate treatment Feed slurry density- control the density. High density will interfere with separation and low density will impact capacity. Each technology will have an optimum feed slurry density

Spirals for coal , iron ore, mineral sands Jigging for coal, iron ore, manganese Shaking tables for mineral sands, gold, cassiterite Centrifugal separators for gold Hindered settling classifiers for coal, iron ore

I Snacked Well That Month I had a partner whose I felt trommel was revolving too fast, and the feed of materials was too quick. He felt that it wasn't. He bet me a month's worth of any snacks of choice that the waste (tailings) would not have a loss of more than .03 grams per ton. I walked over and, within two handfuls, picked out two thumb-tack-size nuggets. The re-washed yield just as much as the first wash. Gravity doesn't only take place in the trommel. It depends on the feed of materials, the speed and grid spacing of the trommel, the nugget trap fill time, the sluice tilt, the type of carpet (if), and the shaking tables or jigs. Consider adjusting angles, tilt, vibrations, speed, density of materials, etc. I snacked well that month.