bauxite processing plant equipment

A bauxite processing plant typically involves several stages to extract alumina (Al₂O₃) from bauxite ore, which is later used to produce aluminum. The key equipment varies depending on the processing method (Bayer Process for refining bauxite or sintering process for low-grade ores). Below is an overview of the essential equipment used in a standard Bayer-process-based bauxite plant:

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1. Crushing & Grinding Equipment

• Primary Crusher: Jaw crusher or gyratory crusher reduces large bauxite lumps (<1m) to smaller fragments (~200mm).
• Secondary Crusher: Cone crusher or impact crusher further crushes material to <30mm.
• Grinding Mills: Ball mills or rod mills grind crushed bauxite into fine powder (~100–300 µm) for digestion.

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2. Digestion (Leaching)

• Digesters: High-pressure vessels (autoclaves) where ground bauxite is mixed with hot sodium hydroxide (NaOH) solution to dissolve alumina.

– Temperature: 140–280°C
– Pressure: Up to 35 bar

• Heat Exchangers: Pre-heat slurry using waste heat from spent liquor.

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3. Clarification & Settling

• Thickeners/Settlers: Separate solid residues (red mud) from sodium aluminate solution.
• Filters: Rotary drum filters or plate-and-frame filters remove residual solids.
• Washers: Counter-current decantation (CCD) washes red mud to recover NaOH.

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4. Precipitation

• Precipitation Tanks: Seeded with fine alumina crystals to promote crystallization of Al(OH)₃ from the clarified solution.

– Temperature: ~50–70°C
– Residence time: Hours to days

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5. Calcination

• Rotary Kilns or Fluidized Bed Calciners: Heat aluminum hydroxide (Al(OH)₃) at ~1000–1200°C to produce pure alumina (Al₂O₃).

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6. Auxiliary Equipment

• Pumps & Pipelines: Transport slurries and liquids between stages.
• Evaporators: Concentrate spent NaOH liquor for recycling.
• Gas Scrubbers: Treat exhaust gases (e.g., SO₂, CO₂).
• Red Mud Disposal Systems: Storage ponds or dry stacking facilities.

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Alternative Processes:

For low-grade/silica-rich bauxite, sintering or combination processes may use:

• Rotary kilns
• Sintering furnaces
• Acid leaching systems

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Would you like details on a specific stage, equipment supplier recommendations, or operational considerations?