A filter press separates solids from liquids by forcing a liquid suspension through a filter medium under pressure, capturing the solids as a filter cake.
A filter press is a widely used piece of industrial equipment designed for solid-liquid separation. It employs pressure filtration to achieve this separation efficiently. The basic operation involves feeding a slurry into the filter press, where the liquid passes through a filter cloth, and the solids are retained.
Key Components of a Filter Press
Understanding the main parts helps explain the process:
- Frame: Provides the structural support for the entire assembly.
- Filter Plates: These are the core elements, often recessed or with chambers. They are pressed together to form sealed compartments.
- Filter Cloth: Placed over each filter plate, this material acts as the filtration medium, allowing liquid (filtrate) to pass through while capturing solid particles.
- Manifold System: Channels the slurry into the plates and the filtrate out of the press.
- Hydraulic Closing System: Applies pressure to hold the plates together, preventing leakage during the filtration cycle.
How the Process Works
The operation of a filter press typically follows a batch cycle:
1. Closing the Press
The filter plates, with filter cloth covering them, are pressed together tightly using a hydraulic system. This creates sealed chambers between the plates.
2. Filling (Slurry Feed)
The slurry (the liquid mixture containing solids) is pumped into the manifold system and enters the empty chambers within the press.
3. Filtration (Pressure Building & Cake Formation)
This is where the separation happens. As the filter press feed pump builds pressure, solids build within the chambers until they are completely chock-full of solids, forming the cake. The liquid phase (filtrate) is forced through the filter cloth, leaving the solid particles trapped on the cloth within the chambers. The filtrate then flows along drainage paths on the plate and exits the press through dedicated filtrate ports. The filtration process continues until the chambers are full of solids and the flow rate of filtrate significantly drops due to the resistance of the formed cake.
4. Cake Washing (Optional)
If required, a wash liquid (like water) can be pumped into the chambers to wash the filter cake and remove any residual impurities from the solids.
5. Air Blowing or Drying (Optional)
Compressed air may be blown through the cake to remove remaining moisture and make the cake drier for easier discharge.
6. Cake Discharge
Once filtration (and optional washing/drying) is complete, the hydraulic pressure holding the plates together is released. The plates are then separated one by one. As the chambers open, the solid filter cake, now solidified, drops out from between the plates, usually falling into a collection bin or conveyor below.
7. Cloth Washing (Optional)
After cake discharge, the filter cloths may be washed in place to remove any remaining solids before starting the next cycle.
Benefits of Using a Filter Press
- High Solids Capture: Effectively separates a large percentage of solids.
- Produces Dry Cake: Often yields a filter cake with relatively low moisture content.
- Simple Operation: Once set up, the cycle is straightforward.
- Robust Design: Durable and reliable for demanding applications.
Applications
Filter presses are utilized in a wide range of industries, including:
- Mining and Minerals Processing
- Wastewater Treatment
- Chemical Manufacturing
- Food and Beverage Production
- Pharmaceuticals
By leveraging pressure, filter presses provide an effective method for separating solid particles from liquid streams, producing both clarified liquid and a dewatered solid cake.
