Sludge dewatering system
Gravity table GTSludge screw presses SCS

Sludge dewatering

Applications for a wide range of dewatering and thickening applications for fibrous and biological paper industry sludges

Proven and effective technology for sludge dewatering applications

The ANDRITZ sludge dewatering system portfolio covers all types of dewatering machines for all fibrous and biological paper industry sludges. Different types of sludges have different dewatering potential. ANDRITZ assists in finding the suitable solution for each and every application.

To evaluate the dewatering characteristics of these sludges, ANDRITZ can test the sludge at its pilot plant in Graz, Austria. As an alternative, a test run at your mill can be arranged by utilizing the ANDRITZ mobile test unit.

Gravity table GT: effective pre-dewatering of sludge with low solids in filtrate

The ANDRITZ gravity table is used as a first dewatering stage for sludge prior to subsequent pressing operations (e.g. pressure filters of sludge screw presses). Gravity is utilized to thicken the sludge from a feed consistency of 0.6–5% to a discharge consistency of 12–22%. The gentle treatment of the gravity table keeps the flocculent consumption low and results in a lower filtrate load compared to other pre-dewatering systems.

Benefits of gravity table GT

  • High thickening capacity
  • Low energy consumption
  • Minimum flocculent consumption
  • Low solids load in filtrate
  • Optional floating roll to increase discharge consistencies

Sludge screw press SCS: highest capacity, highest dryness

The ANDRITZ sludge screw press is designed for high throughput and for high dryness requirements. It utilizes a conical shaft and a decreasing pitch of flights on the screw to dewater sludge through a reinforced screen basket. Backpressure is automatically controlled at the discharge end to prevent blockage and achieve the highest dryness content even with changing sludge characteristics. The addition of a shaft dewatering zone at the end and optional steam heating can bring the sludge dryness up to 70%.

Benefits of sludge screw press SCS

  • Single-line solution with a throughput up to 180 t/d
  • Shaft dewatering for higher final dryness
  • Patented wear shoes to minimize downtime and maintenance costs
  • Optional steam feeding boosts dryness to maximum
  • Self-adjusting backpressure unit
  • Fully closed system
  • Minimal flocculent consumption due to fully automatic control (see: Polyscan)

Continuous pressure filter CPF: for a wide range of sludge dewatering applications

The ANDRITZ continuous pressure filter is a double-wire press with a modular design. By selecting different modules and configurations, the continuous pressure filter allows optimized dewatering of even hard-to-dewater sludges. The continuous pressure filter can be delivered with an integrated pre-dewatering table or, ideally, is combined with the ANDRITZ gravity table.

Benefits of continuous pressure filter CPF

  • Modular design adapts to varying conditions
  • High dryness content of thickened sludge
  • Low specific energy consumption
  • High throughput with excellent filtrate quality
  • Flexible press forces

Flocculent dosing PolyScan+ system: online flocculent control system for sludge dewatering

ANDRITZ developed a patented optically based process control system that works without direct contact with the sludge. Infrared sensors placed at intervals along the length of the gravity zone continuously measure the reflectance of the sludge surface. PolyScan+ then calculates the drainage effectiveness by processing these measurements. The system automatically adjusts the sludge feed, polymer feed, and belt speed to achieve the best drainage at the lowest conditioning costs.

Benefits of ANDRITZ PolyScan+

  • Optimal sludge-to-polymer ratio without operator attention
  • Flocculent savings of 20–30%
  • Constant dryness at the end of sludge dewatering system
  • Lower filtrate solids
  • No over flocculation
  • Control independent of sludge type
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