Membrane filter press
Membrane Filter Press System
The membrane filter press (also called diaphragm filter press) is an advanced variant of the conventional filter press that incorporates flexible, inflatable membranes (diaphragms) in the filter plates. After the initial filtration phase, these membranes are inflated with compressed air or hydraulic fluid to mechanically squeeze the filter cake, significantly reducing residual moisture and producing drier cakes than standard recessed chamber or plate & frame presses. Membrane filter presses are the preferred choice when maximum cake dryness, reduced disposal costs, or improved filtrate recovery are critical.
System Design & Key Components
A membrane filter press features a heavy-duty frame, fixed and movable heads, and a stack of recessed chamber plates where one or both sides of each plate contain a flexible elastomeric membrane. The membranes are typically made of polypropylene, EPDM, or thermoplastic polyurethane and are connected to air/water supply lines. When inflated, they expand into the chamber, uniformly squeezing the cake from both sides.
Filtration & Squeeze Cycle
The complete operating sequence typically includes:
- Plate Closing — Hydraulic ram clamps the plate stack with high force (200–400 bar clamping pressure).
- Chamber Filling / Primary Filtration — Slurry is pumped in at increasing pressure (6–16 bar) until chambers are full and initial cake forms.
- Primary Filtration Phase — Pressure is held; filtrate exits while cake builds and partially dewaters.
- Membrane Squeeze Phase — Membranes are inflated (air pressure 10–20 bar or hydraulic fluid) to mechanically compress the cake, expelling additional liquid.
- Cake Washing (optional) — Wash water is introduced before or between squeeze cycles to displace mother liquor.
- Air Drying / Core Blow — Compressed air blows through to further dry the cake surface and clear ports.
- Plate Opening & Cake Discharge — Plates separate; drier, more rigid cake drops cleanly.
Membrane vs. Conventional Filter Press Comparison
| Feature | Membrane Filter Press | Conventional Recessed Chamber |
|---|---|---|
| Cake Dry Solids Content | 75–90% | 60–80% |
| Residual Moisture Reduction | 10–30% improvement | Baseline |
| Squeeze Mechanism | Inflatable diaphragms | None (pressure only) |
| Best For | Difficult-to-dewater sludges, cost-sensitive disposal | General dewatering, moderate dryness needs |
Typical Operating Parameters
| Parameter | Typical Range | Notes |
|---|---|---|
| Filtration Pressure | 6–16 bar (90–230 psi) | Higher pressures improve primary dewatering |
| Squeeze Pressure | 10–20 bar (air or hydraulic) | Higher squeeze → drier cake |
| Clamping Pressure | 200–400 bar (hydraulic) | Ensures no leakage during high-pressure phases |
| Filter Area | 20–1500 m² | Scalable for industrial-scale applications |
| Cake Dry Solids | 75–90% | Material-dependent; some reach >90% |
Common Applications & Advantages
| Industry / Application | Typical Materials | Primary Benefit |
|---|---|---|
| Mining & Minerals | Tailings, flotation concentrates, red mud | Dry cake for stacking / reduced transport costs |
| Wastewater & Sludge | Municipal biosolids, industrial sludge, digestate | Maximum dryness → lower incineration/landfill costs |
| Chemicals | Pigments, dyes, zeolites, catalysts | High solids recovery, reduced mother liquor loss |
| Food & Beverage | Starch, yeast, fruit/vegetable residues | Drier cake, better product yield |
Key Advantages of Membrane Filter Presses
- Highest achievable cake dryness among filter presses
- Significant reduction in cake volume and disposal costs
- Improved filtrate recovery and washing efficiency
- Shorter overall cycle time in many difficult-to-dewater materials
- More uniform cake structure and easier discharge
- Energy-efficient dewatering compared to thermal drying