What Are Density-Based Stratification and Separation Devices?

Density difference stratification gravity separation equipment is a type of mineral processing equipment that utilizes the density differences between mineral particles to achieve stratification separation in a specific medium (such as water, air, or a high-density medium) through gravity, centrifugal force, or the action of the medium. Its core principle is to create a suitable separation environment so that mineral particles of different densities exhibit differences in settling velocity during their movement, thereby achieving separation. The following is a detailed introduction:

I. Working Principle

1. Stratification Based on Density Difference

Mineral particles in the medium are subjected to gravity, buoyancy, and resistance. Their settling velocity is affected by density, particle size, and medium properties. Heavier particles, which preferentially settle at the bottom of the separation equipment or near the discharge port, while lighter particles settle more slowly and are carried to the tailings end by the medium flow.

2. Separation Environment Design

The impact of density differences on separation can be enhanced by adjusting the equipment structure (such as bed inclination angle, spiral chute pitch) or operating parameters (such as vibration frequency, centrifugal force). Optimizing medium properties (such as density and viscosity) can further improve separation efficiency.

II. Typical Equipment Types

1. Jig Machine

Principle: Utilizes periodic pulsating water flow to stratify mineral particles according to density. Heavy minerals quickly sink to the bottom of the jigging chamber, while light minerals float to the top. Concentrate and tailings are collected separately through discharge devices (such as valves or screens).

Features: Simple structure, high processing capacity (up to hundreds of tons per hour). Suitable for separating ores with a wide particle size range (0.5-30mm). Sensitive to density differences, commonly used for pre-concentration of metal ores such as tungsten, tin, and iron.

2. Vibrating Table

Principle: Achieves stratification of mineral particles according to density and particle size through the reciprocating motion of the table surface and lateral water flow. Heavy minerals move longitudinally along the table surface to the concentrate end, while light minerals are washed to the tailings end by the water flow. Grooves or stripes on the table surface can enhance the stratification effect.

Features: High separation accuracy, capable of producing high-grade concentrates (e.g., gold concentrate grade exceeding 90%). Suitable for fine-grained ores (0.037-2mm). Flexible operation with adjustable parameters to optimize separation.

3. Spiral Chute

Principle: Utilizes the differences in centrifugal force, gravity, and friction as minerals rotate and flow in a spiral chute to achieve stratification. Heavy minerals move along the inner wall of the chute, while light minerals flow outwards. Multiple spiral turns extend the separation path, improving the recovery rate.

Features: Simple structure, no power consumption, low operating cost. Suitable for medium to fine-grained ores (0.06-3mm). Commonly used for separating iron, titanium, chromium, and other metallic ores, as well as recovering gold and platinum.

4. Centrifugal Concentrator

Principle: Enhances stratification based on density differences through centrifugal force generated by high-speed rotation. Heavy minerals rapidly settle onto the inner wall of the rotating drum, while light minerals are discharged. The concentrate is discharged through backwash water, achieving continuous separation.

Features: High separation efficiency and recovery rate (especially suitable for fine-grained minerals). High processing capacity and small footprint. Typically used for recovering precious metals such as gold and silver, and enriching tungsten and tin.

5. Heavy Media Separator

Principle: Uses a dense medium with a density greater than water (e.g., magnetite powder suspension) as the separation medium. Mineral particles in the medium stratify according to density, with heavier minerals sinking and lighter minerals floating. The high-density medium is recovered by screening or magnetic separation for reuse.

Features: High separation accuracy, capable of handling ores with a wide particle size range (0.5-100mm). Suitable for separating minerals with small density differences (e.g., coal and gangue). Requires a supporting (auxiliary) high-density medium recovery system, resulting in higher operating costs.

III. Application Scenarios

Metal Ore Beneficiation: Tungsten, tin, iron, manganese, tantalum, niobium, gold, silver, etc.

Non-metallic Mineral Purification: Coal, graphite, quartz sand, etc.

Precious Metal Recovery: Placer gold mines, platinum group metal mines, etc.

Pre-concentration and Concentration: Used as a roughing device to improve feed grade, or as a concentrator to obtain the final concentrate.

IV. Advantages and Limitations

Advantages

Environmentally friendly and energy-saving: No chemical reagents required, therefore environmentally friendly.

Low cost: Simple equipment structure, easy to maintain.

High adaptability: Capable of processing ores of various particle sizes and densities.

Limitations

There is a limit to the lower limit of the separation particle size (typically >0.03mm).

High requirements for differences in mineral density (typically >0.5g/cm³).

For fine-grained ores, the separation efficiency may be lower than that of flotation or chemical beneficiation methods.