Filtration in ore processing is a crucial solid-liquid separation step used to remove water or other liquids from the concentrated ore slurry, resulting in a drier solid product (filter cake) and a clarified liquid (filtrate). Here’s an overview of its role, methods, and applications:
Purpose of Filtration in Ore Processing
1. Dewatering: Reduces moisture content in concentrates (e.g., metal sulfides, iron ore) for easier handling, transport, or further processing (e.g., smelting).
2. Recovery of Process Liquids: Recycles water or chemicals (e.g., leaching agents) back into the circuit.
3. Waste Removal: Separates tailings from process water for disposal or environmental compliance.
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Common Filtration Methods
1. Vacuum Filtration
– Equipment: Drum filters, disc filters, horizontal belt filters.
– Process: A vacuum sucks liquid through a porous filter medium, leaving solids behind.
– Applications: Iron ore, copper concentrates, coal.
2. Pressure Filtration
– Equipment: Plate-and-frame filter presses, membrane filter presses.
– Process: High pressure forces liquid through the filter cloth, yielding very dry cakes (low moisture content).
– Applications: Precious metals (gold/silver concentrates), zinc/lead concentrates.
3. Centrifugal Filtration
– Equipment: Centrifuges (screen bowl or basket types).
– Process: Centrifugal force separates solids from liquids.
– Applications: Fine particles (e.g., kaolin, alumina).
4. Gravity Filtration
– Used for coarse particles or low-volume applications (e.g., heap leach discharge).
Factors Influencing Filtration Efficiency
– Particle Size & Shape: Fine particles (e.g., clay) may require flocculants to improve filtration.
– Slurry Density: Higher solids content improves throughput but may clog filters.
– Filter Media Selection: Cloth/material must resist abrasion and chemical corrosion.
– Pressure/Vacuum Levels: Higher pressure reduces moisture but increases energy costs.
Challenges
– Blinding/Fouling: Fine particles clog filter media; backwashing or chemical cleaning may be needed.
– High Moisture Content: Some ores (e.g., laterites) are difficult to dewater fully.
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