What is a Poly Disc Filter?
A Poly Disc Filter is a vacuum-based filtration equipment used in paper mills for white water recovery, fiber saving, and low-consistency pulp thickening.
It consists of multiple plastic (polypropylene) filter discs mounted on a rotating shaft, partially submerged in a slurry tank.
It is widely used in stock preparation, save-all systems, and approach flow of paper & board machines.
Working Principle of Poly Disc Filter
The operation is based on vacuum filtration and gravity drainage.
Step-by-Step Working:
- Slurry Feeding:
- White water or dilute pulp slurry (0.1–1.2% consistency) enters the filter vat.
- The discs are partially submerged in the slurry.
- Vacuum Application
- Vacuum is applied inside each disc sector.
- Water passes through the filter cloth into the disc, while fibers are retained on the surface.
- Fiber Cake Formation
- A thin fiber mat forms on the disc surface, improving filtration efficiency.
- Cake Dewatering
- As the disc rotates out of the slurry, vacuum continues, further dewatering the fiber mat.
- Cake Discharge
- A blowback (compressed air) or doctor blade removes the fiber cake.
- Thickened pulp is discharged to the accepts chest.
- Filtrate Collection
- Clear filtrate (white water) is collected and reused in showers, dilution, or stock preparation. Typical Operating Parameters
| Parameter | Range |
| Feed consistency | 0.1 – 1.2% |
| Discharge consistency | 8 – 12% |
| Filtrate clarity | < 100–150 ppm SS |
| Disc speed | 0.5 – 2 rpm |
| Vacuum level | 400 – 600 mmHg |
Applications in Paper Mills
White water recovery (save-all system)
Fiber recovery from paper machine backwater
Pulp thickening before storage or further cleaning
Broke handling systems
Approach flow water reuse
Board machines (top & bottom layer furnish saving)
“Especially useful in high-speed paper machines and multi-layer board machines, where fiber loss control is critical.”
Advantages of Poly Disc Filter
High fiber recovery efficiency
Compact design (less floor space than drum filters)
Low power consumption
Continuous operation
High filtrate clarity
Plastic discs – corrosion resistant
Suitable for recycled fiber systems
Low maintenance (few moving parts)
Limitations of Poly Disc Filter
Higher capital cost than simple save-all systems
Filter cloth blinding if stickies or pitch are high
Requires stable feed consistency
Not effective for very fine fillers without chemical aid
Periodic cloth cleaning / replacement needed
Vacuum system maintenance required
Comparison with Other Save-All Systems
| System | Efficiency | Space | Cost |
| Poly Disc Filter | Very High | Low | High |
| Drum Save-All | Medium | High | Medium |
| DAF System | High | Medium | Medium |
| Sedimentation | Low | High | Low |
ANDRITZ India Pvt. Ltd.
Valmet India
Voith Paper India
Kadant India
SULZER / Ensival Moret
Indian Manufacturers & Supplier Parason Machinery (India) Pvt. Ltd. Eros Envirotech Shree Krishna Paper Machinery Hi-Tech Engineers PAP-TECH Engineers
“Indian suppliers usually offer cost-effective solutions with local service support.”
Conclusion
A Poly Disc Filter is an essential high-efficiency fiber recovery and water reuse system in modern paper and board mills.
It significantly reduces fiber loss, fresh water consumption, and effluent load, making it a key equipment for cost reduction and sustainability.