Industrial Filtration Equipment: Types and Operation
1. Plate and Frame Filter
Definition
A plate and frame filter is a pressure filtration equipment used to separate solids from liquids by passing the slurry through filter cloths placed between plates and frames.
Construction
It consists of alternate plates and frames made of cast iron or stainless steel. Each plate is covered with a filter cloth. The frames provide space for solid (cake) collection. The whole assembly is held tightly in a press with inlet and outlet connections.
Working
The slurry is pumped under pressure into the filter press. The liquid passes through the filter cloth and exits as filtrate, while the solid particles are retained in the frames forming a filter cake. After filtration, the press is opened and the cake is removed.
Uses
- Clarification of pharmaceutical liquids
- Filtration of syrups, injections, and antibiotics
- Separation of crystals from mother liquor
2. Plate Leaf Filter
Definition
A plate leaf filter is a pressure filter in which filtration occurs on flat or vertical leaves covered with filter cloth.
Construction
It consists of a closed cylindrical vessel containing several metal leaves (plates). Each leaf is covered with a filter medium and connected to a common outlet pipe.
Working
Slurry enters the vessel under pressure. Liquid passes through the filter cloth and leaf surface, while solids form a cake on the leaf. The filtrate flows through the hollow leaves and is collected. Cake is removed by vibration or washing.
Uses
- Filtration of viscous liquids
- Decolorization of pharmaceutical solutions
- Filtration of oils and syrups
3. Drum Filter (Rotary Vacuum Drum Filter)
Definition
A drum filter is a continuous vacuum filtration equipment used to separate solids from liquids.
Construction
It consists of a rotating hollow drum partially immersed in slurry. The drum surface is covered with a filter cloth and connected to a vacuum system.
Working
As the drum rotates, vacuum draws the liquid through the cloth, forming a solid cake on the surface. The cake is dried by vacuum and then removed using a scraper blade.
Uses
- Continuous large-scale filtration
- Filtration of antibiotics and fermentation broths
- Separation of crystalline solids
4. Perforated Basket Centrifuge
Definition
A perforated basket centrifuge is a filtration centrifuge used to separate solids from liquids using centrifugal force.
Construction
It consists of a rotating perforated basket lined with a filter cloth and enclosed in a casing.
Working
Slurry is fed into the rotating basket. Due to centrifugal force, liquid passes out through the perforations, while solids are retained on the cloth as a cake.
Uses
- Separation of crystals
- Dewatering of solids
- Used in chemical and pharmaceutical industries
5. Non-Perforated Basket Centrifuge
Definition
A non-perforated basket centrifuge is a sedimentation centrifuge used to separate solids based on density difference.
Construction
It consists of a solid (non-perforated) rotating bowl without holes.
Working
When slurry is introduced, heavier solids settle on the wall of the bowl due to centrifugal force, while the clarified liquid forms an inner layer and is removed separately.
Uses
- Clarification of liquids
- Separation of fine particles
- Used for emulsions and suspensions