Filter Belts vs Conveyor Belts
Filter belts are fundamentally different from conveyor belts despite both being endless rubber-fabric belts. A conveyor belt is designed to be impermeable β?to carry material without leakage. A filter belt is designed to be permeable β?to allow liquid to pass through while retaining solid particles. The selection criteria are completely different.
How Belt Filter Presses Work
A belt filter press uses two permeable fabric belts that sandwich a slurry between them. The slurry enters between the belts, free liquid drains through the fabric by gravity, then the belts pass through a series of rollers that squeeze the remaining liquid out of the cake. The dewatered cake is discharged as the belts separate.
In mineral processing, belt filter presses are used for: concentrate dewatering (copper, zinc, lead concentrates), coal fines dewatering, tailings dewatering, and red mud (bauxite residue) dewatering.
Filter Belt Fabric Selection
Polyester Monofilament
The most common choice for mineral processing:
- Good dimensional stability β?maintains accurate aperture size under tension
- Chemical resistance β?withstands dilute acids and alkalis in most mineral process circuits
- Low cake adhesion β?cake releases cleanly
- Typical applications: copper concentrate, zinc concentrate, coal fines
Polypropylene
- Superior chemical resistance β?suitable for highly acidic or alkaline slurries
- Lower cost than polyester
- Slightly lower dimensional stability under tension
- Typical applications: acid mine drainage dewatering, red mud, strongly acidic slurries
Permeability Selection
Permeability (measured in CFM β?cubic feet per minute per square foot of fabric at 0.5" water pressure) must be matched to the particle size distribution of the slurry:
| Permeability (CFM) | Particle Size | Typical Application |
|---|---|---|
| 200β?00 CFM | Fine (<50 micron) | Mineral concentrate, fine coal |
| 400β?00 CFM | Medium (50β?00 micron) | Coal fines, mixed mineral slurries |
| 600β?00 CFM | Coarse (>200 micron) | Coarse coal, aggregates dewatering |
Filter Belt Maintenance
Filter belt permeability decreases over time as fine particles blind the fabric openings. Maintenance requirements:
- High-pressure water wash: Automatic wash bars on both belt sides after cake discharge β?60β?00 bar water pressure
- Chemical cleaning: Periodic acid wash (dilute HCl or HF) to dissolve mineral scale; alkali wash for organic foulants
- Permeability monitoring: Measure filtrate flow rate weekly β?declining filtrate indicates blinding
- Belt replacement interval: Typically 6β?8 months depending on slurry chemistry and cleaning regime
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