Outotec® Clarifiers

Outotec High Rate Thickeners and Clarifiers

Outotec High Rate Thickeners and Clarifiers suit all applications where flocculants can be used in the process. Also ideally suited to clarifying, with the addition of increased sidewall height, deeper feedwell and other special features.

External underflow recycling is sometimes used to improve floc formation and particle capture.

  • „„ Outotec Vane Feedwell
  • „„ Controlled solids inventory
  • „„ High throughput per unit area
  • „„ Free standing or on-ground tanks
  • „ Short retention time
  • Optional underflow recycle
  • Clear overflow

Thickener 3dControlling the thickening process is based around two important and dependent functions:

  • Control of the flocculation process,
  • Control of solids inventory in the thickener tank.

Controlling the flocculation process requires the production of flocculated aggregates that are of a consistent size and density, thus maintaining the required settling rate and solids compaction rate in the thickener.

Controlling the solids inventory means using the underflow pumps to maintain a steady state mass of solids in the settled bed of the thickener.

If these two conditions can be achieved, the thickener will produce a consistent underflow density, rake torque and overflow clarity, while minimizing flocculant consumption.

Pilot plant testing

Outotec supplies pilot scale thickening and clarifying equipment backed by trained, highly experienced personnel, to meet any process requirement. The size and configuration of the equipment is based on material characteristics and performance goals. Outotec has a comprehensive range of pilot plant units for conventional settling, high rate thickening and/or clarifying, high compression and also paste thickening. A feed rate of 1-8m3/h (4.4-35.2 US gpm) of pulp is required for the pilot plant thickener/clarifier.

Testing is required for the selection of correct thickener or clarifier size and configuration for each customer’s application. Outotec is renowned for its professional testing service using cylinder settling tests, continuous dynamic bench-scale tests and pilot plant tests.

The method used to accurately determine the size and expected performance of Outotec High Rate Thickeners and Clarifiers is dynamic bench or pilot scale testing, as static settling tests do not adequately simulate the high rate principle.

Bench-scale testing

Continuous bench-scale tests are performed in our 100 mm (4”) diameter dynamic thickener or clarifier at site or in our laboratories. A sample of slurry containing 10–25 kg (22–55 lb) of solids is all that is required for a series of tests to determine underflow density and overflow clarity for a range of feed rates and flocculant dosages.

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