Filter Press vs Belt Filter: Cake Moisture, Cycle Time and Labour
Filter presses produce the driest cake and the clearest filtrate of any common dewatering device, but they are batch machines that need operator attention. Belt and vacuum filters run continuously with lower labour but leave more moisture in the cake. Decide with the downstream step, not with the filter itself.
Comparison
| Item | Plate & frame filter press | Belt / vacuum filter |
|---|---|---|
| Operation | Batch — fill, press, blow, discharge | Continuous |
| Typical cake moisture | 8–20% (with membrane squeeze and air blow) | 18–35% |
| Filtrate clarity | Excellent — cloth acts as depth filter | Moderate — fines pass early |
| Solids in feed | 1–40% w/w | Usually >10% for belt |
| Labour | Higher — cloth washing, plate inspection | Lower — but continuous supervision of tracking and vacuum |
| Scale-up | Add plates/chambers; easy to oversize | Width × speed; sensitive to fines |
| Wash efficiency | Good — counter-current wash in chambers | Moderate — displacement wash on belt |
Decision rules
If the cake goes to smelting, leaching again, or transport: moisture is money. A membrane filter press with air blow typically saves several percentage points of moisture versus a belt filter, which can repay the labour cost within a year at tonnage.
If the cake is waste going to tailings: belt or vacuum filtration is usually enough, and continuous operation avoids buffer tanks.
If the feed varies in solids or contains coarse fast-settling particles: a filter press handles it with a longer fill; a belt filter will track badly and lose vacuum.
Practical notes from pilot work
Filter cloth selection often matters more than the machine. A blinded cloth halves throughput and raises moisture regardless of pressing pressure. Run a leaf test on your actual slurry before specifying: it gives cake thickness, cycle time and expected moisture, which is the only reliable basis for sizing.
Send the slurry solids, PSD and target moisture, and we will size a press with the chamber count and cloth specification, or confirm that a belt filter meets the downstream limit.