Plate and Frame Filter Press
Plate and Frame Filter Press System
The plate and frame filter press is a classic and versatile solid-liquid separation device that uses alternating flat filter plates and hollow frames to form filtration chambers. Slurry is pumped into the frames under pressure, solids are retained as cake inside the frames, and clear filtrate passes through the filter cloths covering the plates. While largely replaced by recessed chamber and membrane presses in many modern applications, plate and frame designs remain popular for smaller-scale operations, specialty filtrations, and when thinner cakes or easier cloth replacement are desired.
System Design & Components
The plate and frame filter press consists of a sturdy side-bar or overhead-beam frame, a fixed head, a movable hydraulic closing head, and a stack of alternating filter plates and frames. Each plate is covered on both sides with filter cloth and features drainage grooves/channels leading to corner ports. Frames are open in the center, creating the chamber volume where cake forms. When clamped together, the stack forms sealed filtration chambers fed through corner or center feed ports.
Filtration Cycle
The typical operating sequence includes:
- Plate & Frame Closing — Hydraulic ram clamps the entire stack tightly to prevent leakage (clamping force 100–300 bar).
- Chamber Filling — Slurry is pumped into the frames through feed ports at increasing pressure (typically 4–12 bar).
- Filtration Phase — Liquid passes through the cloths on both adjacent plates while solids deposit inside the frame cavity.
- Cake Washing (optional) — Wash liquid is introduced through separate wash ports to displace mother liquor.
- Air Drying / Blow-Down — Compressed air is blown through to remove residual moisture and clear filtrate channels.
- Plate Opening & Cake Discharge — Plates and frames separate sequentially; cake drops by gravity (often assisted by manual scraping or vibration in older models).
Plate & Frame vs. Recessed Chamber Comparison
| Feature | Plate & Frame | Recessed Chamber |
|---|---|---|
| Cake Formation Location | Inside frame cavity only | Inside recessed area of plates |
| Typical Cake Thickness | 10–50 mm (frame thickness) | 25–50 mm |
| Dry Solids Content | 55–75% | 60–80% |
| Cloth Replacement Ease | Easier (plates are flat) | More difficult (recessed shape) |
| Typical Use Case | Smaller systems, specialty filtration | Large industrial dewatering |
Typical Operating Parameters
| Parameter | Typical Range | Notes |
|---|---|---|
| Filtration Pressure | 4–12 bar (60–175 psi) | Lower than modern recessed presses |
| Clamping Pressure | 100–300 bar (hydraulic) | Ensures tight seal between plates & frames |
| Filter Area per Press | 5–400 m² | Common in smaller to medium-scale operations |
| Cake Dry Solids | 55–75% | Depends on slurry and cycle time |
Common Applications & Advantages
| Industry / Application | Typical Materials | Primary Goal |
|---|---|---|
| Chemicals & Pigments | Dyes, pigments, fine chemicals, salts | Solids recovery, mother liquor separation |
| Food & Beverage | Fruit juice clarification, wine lees, starch, sugar syrup | Clarification, polishing |
| Pharmaceuticals | API intermediates, herbal extracts | High-purity cake, contained operation |
| Ceramics & Clay | Kaolin, bentonite, ceramic slips | Dewatering for reuse or disposal |
Key Advantages of Plate and Frame Filter Presses
- Simple, proven design with long history of reliability
- Flat plates make filter cloth easier and cheaper to replace
- Flexible cake thickness (determined by frame size)
- Good for smaller-scale or specialty filtration tasks
- Excellent filtrate clarity when properly clothed
- Lower capital cost compared to fully automated recessed or membrane presses