Gravity Separation Equipment: Core Technology Analysis and Practical Mineral Processing Guide

Gravity separation, which achieves mineral separation based on density differences, represents the most cost-effective and environmentally compatible method in mineral processing. With recent technological innovations and expanded application boundaries, its value in mineral processing has become increasingly prominent. This article systematically examines the core value of gravity separation processes, mainstream equipment selection, process efficiency parameter control, and equipment maintenance strategies, providing practical mineral processing guidelines for mining enterprises.

Fundamental Value and Application Boundaries of Gravity Separation

Gravity separation offers unique advantages in mineral processing, with its core value manifested in three aspects:

- Zero Chemical Reagent Dependency: The entire process uses water as the medium, allowing tailings to be discharged directly without environmental pollution risks

- Coarse Particle Pre-rejection: Eliminates 30%-50% of waste rock after crushing, reducing grinding energy consumption by over 35%

- Wide Particle Size Adaptability: Effectively recovers minerals from placer gold (>0.1mm) to fine-grained cassiterite (0.02mm), particularly suitable for small and medium-sized mining investments

Gravity separation processes have broad applicability in processing different types of mineral resources:

- Placer Deposits: Coastal sand ilmenite, rare earth sand deposits — using spiral chute + shaking table combinations

- Vein Deposits: Tungsten-tin quartz veins, hematite — requiring jig machines for roughing + shaking tables for cleaning

However, gravity separation also has application limitations: when the density difference between minerals and gangue is <0.5g/cm³, separation efficiency decreases significantly, necessitating combined magnetic separation or flotation techniques.

Mainstream Equipment Selection and Operation Essentials

As high-capacity, structurally simple gravity separation equipment, spiral chutes are widely used in primary separation:

- Particle Size Compatibility Range: Optimal separation particle size 0.1-2mm; coarser particles may cause clogging, while finer particles lead to sharp drops in recovery rates

- Model Selection Criteria (based on feed capacity):

2-3t/h → LL900 model (900mm diameter, 4-start design)

8-16t/h → DL1500 model (1500mm diameter, 5-start design)

15-40t/h → DL2000 model (2000mm diameter, 6-start design)

- Golden Operating Parameters:

Feed concentration controlled at 30%-35%; higher concentrations cause stratification disorder

Wash water pressure 0.05-0.1MPa; insufficient pressure increases light mineral entrainment by 15%

Shaking tables are key equipment for achieving high-precision separation in gravity concentration processes:

- Particle Size Classification Selection Principles:

>0.2mm → Coarse sand shaking tables (deck riffles 3mm high, stroke length 16mm)

0.074-0.2mm → Fine sand shaking tables (deck riffles 1.5mm high, 320 strokes/min)

<0.074mm → Slime shaking tables (with additional concentrate wash water, stroke length 8mm)

- Capacity Management (using tin ore as an example):

Coarse sand shaking tables (0.5-0.2mm) — 0.8-1.0t/h capacity

Slime shaking tables (0.074-0.04mm) — only 0.2-0.3t/h capacity

- Space Optimization Solutions: Multi-deck shaking tables (3-4 stacked decks) save 60% of floor space compared to single-deck tables but require simultaneous improvement in feed uniformity

Vibrating gravity concentrators represent a breakthrough in gravity separation technology for fine particle processing:

- Technological Breakthrough: Synergistic combination of gravity + vibrational energy + liquid buoyancy, extending the separation limit down to 5 microns

- Key Parameter Control:

Coarse particles (>0.1mm): Amplitude 3-5mm, frequency 15Hz

Fine particles (<0.02mm): Reduced amplitude to 1mm, increased frequency to 25Hz

- Anti-clogging Design Features: Sand discharge pipes equipped with vibration isolation hoses, vibration container featuring a butterfly-shaped structure with raised edges and a depressed center

Core Parameter Control for Process Efficiency Enhancement

Classification is a key prerequisite for improving gravity separation efficiency:

- Spiral chutes should be preceded by hydrocyclone groups (3 stages in series), ensuring that particles finer than 100 mesh account for >85% of the feed

- Shaking table feeds require narrow size range separation (e.g., 0.1-0.2mm processed separately); mixed particle sizes cause recovery rate decreases of 12%

Water control is fundamental to the stable operation of gravity separation processes:

- Supplementary Water Classification Control:

Jig machine hutch water pressure >0.2MPa, forming a stable bed layer

Shaking table transverse water flow velocity 0.8-1.2m/s; flow velocity deviations >10% intensify concentrate grade fluctuations

For difficult-to-separate minerals, density control can significantly improve separation results:

- Heavy medium vibrating trough suspension liquid density requires dynamic stability (fluctuation <0.05g/cm³), adding magnetite powder (>90% finer than 200 mesh) as a densifier

Equipment Maintenance and Lifespan Extension Strategies

Selecting appropriate wear-resistant materials can significantly extend equipment service life:

- Spiral Chute Linings: For acidic slurry environments, use nitrile rubber (Shore A85 hardness), with service life twice that of polyurethane

- Shaking Table Decks: Fiberglass substrate + silicon carbide coating (wear resistance index 180%), avoiding deformation problems of traditional wooden decks

Preventive maintenance is key to extending equipment lifespan:

- Lubrication Management:

Shaking table eccentric shaft bearings require greasing every 8 hours, using molybdenum disulfide lithium-based grease (for high-temperature conditions)

Spiral chute center columns require quarterly cleaning to prevent hardened slurry jamming

- Wear Part Regeneration Techniques:

Jaw plate rotation: After 30% wear on one side, rotate left and right sides, extending lifespan by 40%

Liner hardfacing repair: Repair localized wear using tungsten carbide welding rods, costing only 35% of new parts

- Resonance Prevention: Install rubber vibration damping pads (≥50mm thickness) under equipment foundations; stop and level the equipment when amplitude exceeds specifications

Equipment requires corresponding adaptability modifications for different operating conditions:

- Install automatic drainage valves in motor junction boxes in high-humidity mining areas

- In dusty conditions, modify bearing housings to use labyrinth + lip double seals, reducing dust penetration rates by 90%

Conclusion: Back to Basics and Future Outlook for Gravity Separation Technology

The core competitive advantage of gravity separation processes remains the simplicity of physical separation and economic operating costs. Through precise particle size control (hydraulic classification), equipment parameter optimization (slope/stroke frequency), and preventive maintenance measures, gravity separation methods can achieve comprehensive recovery rates above 75% even in fine particle recovery applications (-20 microns).

Future technological evolution will focus on compound force field synergy (such as vibration-gravity fields) and wear-resistant material upgrades, further expanding the application boundaries of gravity separation technology in complex associated mineral resource utilization. As environmental requirements become increasingly stringent, gravity separation technology, with its environmentally friendly characteristics, will play an even more important role in mineral processing.