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Froth Flotation Cell
Brief description
An advanced mineral processing vessel that separates target metallic ore minerals from worthless crushed gangue rock. By bubbling compressed air through a stirred chemical pulp slurry, hydrophobic target mineral particles cling to rising air bubbles, forming a concentrated froth overflow while waste material sinks.
Use / Function
- Primary Use: Concentration of low-grade sulfide ores (copper, lead, zinc, nickel, molybdenum) and iron ore.
- Secondary Uses: Recycling paper fibers, separating microplastics, and purifying fine industrial coal dust.
- Scale: Industrial mineral processing plants and metallurgical refining facilities.
Operating principle
- Slurry Preparation: Crushed, finely ground mineral ore is mixed with water to form a fluid pulp mixture inside an open tank.
- Collector Chemical Addition: Surfactant collector chemicals (such as xanthates or pine/vegetable oil derivatives) are added, coating target mineral grains to render their surface hydrophobic (water-repellent).
- Air Dispersion and Agitation: A high-speed central impeller thoroughly agitates the pulp while injecting fine micro-bubbles of compressed air throughout the tank.
- Bubble Attachment: Hydrophobic target mineral particles attach selectively to rising air micro-bubbles, while hydrophilic gangue rock remains suspended or sinks to the bottom.
- Froth Skimming: A stable mineralized foam accumulates on the fluid surface and is continuously scraped off by rotating paddles into discharge launders for smelting.
How to create it
- Build Tank Shell: Fabricate a deep rectangular or cylindrical vessel from welded steel plate or wood lined with waterproof sealant.
- Mount Central Shaft and Rotor: Install a vertical drive shaft fitted with a bladed impeller at the bottom center of the tank.
- Install Air Induction Tube: Run a hollow central shroud or pressurized air line surrounding the impeller shaft to supply steady air flow to the agitation zone.
- Fabricate Overflow Launder and Skimmers: Attach side collection troughs and motor-driven rotating rubber paddle wheels along the top edges to scrape off accumulated foam.
- Connect Slurry Feed and Underflow Discharge: Position an inlet feed box on one side and an adjustable height tailing discharge weir at the opposite bottom corner.
Materials needed
- Cell Vessel: Welded Steel sheet or treated Wood tank.
- Impeller Drive: Steel shaft and abrasion-resistant cast rotor.
- Process Fluids: Water for slurry suspension and Vegetable Oil or organic collectors/frothers.
Variants and improvements
- Sub-Aeration Flotation Cell: Mechanically driven submerged rotor pulls atmospheric air down a hollow standpipe without needing external air compressors.
- Column Flotation Cell: Tall vertical pipe column using spargers at the bottom to produce micro-bubbles with counter-current wash water for high purity concentrates.
- Pneumatic Flotation Cell: Aeration occurs outside the main tank in high-shear mixers prior to rapid froth discharge.
Limits and risks
- Chemical Toxicity: Collector and frother chemicals can pose environmental contamination risks if wastewater tailings are not contained.
- Fine Particle Sensitivity: Requires very fine ore grinding (typically under 100 microns); overly coarse grains fail to float.
- Mechanical Abrasion: Slurry rapidly wears down impellers, stator vanes, and pump liners, requiring frequent maintenance.