FAQ - filter press
Operating a filter press
The filter press operates discontinuously: solids are separated from liquids in several process steps. For optimal results, both a robust machine and a well-developed process technology are required.
Equipment
- Filter press with hydraulic system and transport device for opening the chambers.
- Chamber filter plates made of polypropylene (light, cost-effective) or cast steel (high temperature resistance, heavy and expensive).
- Filter cloths, crucial for separation and cake release (usually polypropylene, thermally fixed, accurately fitted).
- Fittings for sludge, wash water, filtrate, and compressed air.
- Feed pump with pressure and flow control.
- High-pressure washing system (up to 100 bar) for cleaning cloths.
- Acid washing system for chemical removal of lime deposits.
Operation and Control
Feed pump:
- Typically progressive cavity, diaphragm, or rotary lobe pumps.
- Operated via frequency converter.
- Controlled by pressure, flow rate, and batch input.
- Key parameters: max. pressure, start-up behavior, filtrate curve, shutdown conditions.
Cleaning:
- High-pressure washing depending on sludge composition and batch frequency (interval: once per week to once per shift).
- Chemical cleaning with diluted hydrochloric acid against lime deposits, often with recirculation.
Control system:
- PLC-controlled, with LCD visualization.
- Continuous monitoring and documentation of pressure, flow, and temperature.
- Easy parameter adjustment required.
- Automated systems ensure more consistent results and simplify operation.
Process Technology of a Filter Press
A batch cycle consists of four main steps:
- 1. Closing the filter press
- 2. Filtering the sludge
- 3. Drying the filter cakes
- 4. Opening and discharging
1. Closing the filter press
Chambers are sealed hydraulically with defined closing force.
- Elements must be clean, correctly aligned, and stress-free.
- Hydraulic pressure is monitored and automatically regulated.
- Excessive force can damage plates and cloths.
2. Filtering the sludge
Initially, the flow rate is high; later, pressure rises and pump capacity decreases.
- Pump should start with soft-start; controlled via frequency converter.
- Uniform chamber filling is crucial for cake washing and element lifetime.
- Filtration parameters (pressure, flow, input) must be adjustable in the control system.
- Knowledge of sludge composition is essential for optimal settings.
3. Drying the filter cakes
Capillary water is blown out with compressed air at the end.
- Uniform cake improves drying quality.
- Air pressure and drying time must match material requirements.
- Control must allow simple parameter adjustments.
4. Opening and discharging
After pressure release, the press is opened, and cakes usually fall out automatically.
- Filter cloths must be clean; regular high-pressure or chemical cleaning is required.
- Operators monitor discharge and adjust setup parameters if needed.
- Laboratory samples (1–2 per shift) ensure solids content quality control.