The plate and frame filter is a widely used filtration system in the pharmaceutical, chemical, food, and beverage industries. It is commonly used to separate solids from liquids, particularly in applications requiring high purity and clarity.
1. Definition
A plate and frame filter is a type of pressure filter where the filtration process occurs through filter media supported on a series of plates and frames arranged alternately. The filter media (usually filter cloths) are placed between the plates and frames to retain solids and allow filtrate (filtered liquid) to pass through.
2. Principle
The plate and frame filter operates based on pressure-driven filtration. Liquid is forced through a filter medium by applying pressure, allowing the fluid (filtrate) to pass through while retaining the solid particles (filter cake) on the surface of the filter medium. The primary principle involves alternating plates and frames that create chambers for holding filter cloths, which separate solids from liquids.
3. Construction
The plate and frame filter consists of the following main components:
Frames and Plates: Arranged alternately, frames hold the unfiltered liquid, and plates provide support for the filter cloth. Each plate and frame has a series of grooves and ribs to aid the filtration process.
Filter Cloth or Media: This medium is placed between the plates and frames. It acts as a barrier that retains solid particles while allowing the liquid to pass through.
Feed Channel: A feed channel runs through the entire length of the filter unit, allowing unfiltered liquid to enter each frame.
Filtrate Outlets: Small outlets on each plate collect and discharge the filtered liquid.
Pressure System: A pump or pressure source applies force, pushing the liquid through the filter.
Clamping Mechanism: A mechanical or hydraulic clamping system holds the plates and frames together tightly, preventing leakage and maintaining uniform pressure.
4. Working
The working of a plate and frame filter involves the following steps:
1. Feed Inlet: The slurry or unfiltered liquid is pumped into the filter unit through the feed channel, filling each frame.
2. Filtration Process: Under applied pressure, the liquid passes through the filter cloth, which retains the solid particles on its surface, forming a filter cake within the frames.
3. Filtrate Collection: The filtered liquid, now free of solids, passes through the filter cloth, flows into the plate’s grooves, and exits through the filtrate outlet.
4. Cake Discharge: After a certain period, the filtration process is stopped, and the unit is opened to remove the filter cake from the frames manually or by backwashing.
5. Cleaning and Reassembly: Once the cake is removed, the filter cloths and plates are cleaned, reassembled, and prepared for the next filtration cycle.
5. Uses
The plate and frame filter has several applications across industries:
Pharmaceutical Industry: Used for clarifying liquids, removing impurities from serums, antibiotics, and other injectable products.
Food and Beverage Industry: Employed for purifying edible oils, juices, and wine to remove suspended particles.
Chemical Industry: Used for filtering solutions and separating solids from high-viscosity liquids.
Biotechnology: Filters out biomass from fermentation broths and separates fine particulates from liquid products.
Wastewater Treatment: Effective for removing suspended solids and impurities from industrial wastewater.
6. Merits
The plate and frame filter offers several advantages:
High Clarity Filtration: Provides excellent filtration quality with minimal particle contamination in the filtrate.
Suitable for Viscous Fluids: Capable of handling high-viscosity liquids and fluids with high solid content.
Reusable Filter Media: Filter cloths or media can be washed and reused, reducing operational costs.
Adjustable Pressure: Pressure can be adjusted based on the filtration requirements and characteristics of the liquid.
Modular Design: Plates and frames can be added or removed to adjust the capacity, making it adaptable for different scales of operation.
7. Demerits
Despite its advantages, the plate and frame filter also has limitations:
Time-Consuming: Requires manual cleaning and cake removal, which increases downtime between cycles.
High Labor Requirement: Filter cake discharge and filter cloth cleaning are labor-intensive, requiring manual intervention.
Pressure Limitations: Not suitable for extremely high-pressure applications, as leakage may occur between plates.
Filter Cloth Clogging: Fine particles or viscous liquids can cause clogging, requiring frequent cleaning and maintenance.
Space Requirement: Takes up more space compared to other filtration systems due to its large plate and frame assembly.
| Aspect | Plate and Frame Filter |
| Definition | A type of filter where solids and liquids are separated by applying pressure, with filtration occurring through filter media placed between plates and frames. |
| Principle | Pressure-driven filtration through filter cloth; solids are retained while liquid passes through. |
| Construction | Alternating plates and frames, filter cloth, feed channel, filtrate outlets, clamping mechanism, and pressure system. |
| Working | Feed inlet, filtration, filtrate collection, cake discharge, and cleaning steps. |
| Uses | Clarification in pharmaceuticals, food/beverage purification, chemical separation, biotechnology, and wastewater treatment. |
| Merits | High clarity, suitable for viscous fluids, reusable filter media, adjustable pressure, and modular design. |
| Demerits | Time-consuming, labor-intensive, pressure limitations, filter cloth clogging, and large space requirement. |
Conclusion
The plate and frame filter remains a valuable filtration method in the pharmaceutical and other industries due to its effective solid-liquid separation capabilities. While it does require significant manual labor and regular maintenance, its ability to achieve high-purity filtration makes it an indispensable tool for processes where clarity and quality are paramount. Proper understanding of its design, working principles, and maintenance requirements allows for its efficient use in various filtration applications.
