Centrifuge


Centrifuge

  • Apply the basis of sedimentation of two substances with different densities
  • Could be separation of solid/solid, liquid/liquid or solid/liquid
  • Separation completed through centrifugal forces arise from continuous rotation
  • Feed flow ranges from 1.5 to 12.0 litre/second (depend on applications)
  • Rotational speed are commonly in the range of 1000 to 6000 rpm
  • Offers one major advantage over the belt press, and that is that high solids capacities can be achieved in a very compact unit

Sludge thickening using centrifugal force is one of the common processes that can be applied to reduce the water content and thus thickens the sludge. There are basically two different types of centrifuge designed for the application and both methods rely on the same principal to separate out the liquid and solid content. First is the “solid bowl centrifuge”, which is placed horizontally and during the operation, wastewater wet sludge will be continuously fed into the unit. The moving shaft actually has a set of helical scrolls, which will act to push the solid waste towards the other end, far away from the liquid moving towards another direction. As solid content starts to collect and build up, soon enough the accumulated sludge will become just too heavy and then drops down to a collection bin.

 

Unlike the solid bowl centrifuge, which is based on continuous operation, the “imperforate basket” is a batch process, which will need operators’ intervention to handle and remove accumulated sludge. Compared to solid bowl which has a helical scroll that automatically push and separate out the sludge, solid build up that accumulates on the vertical surface of the imperforate basket will accumulate there until it reaches a certain holding capacity before the bowl decelerates. During this, a scraper can be used to remove out the sludge inside it before everything goes back to normal operation. For both methods, in order to achieve good separation, usually polymers can be mixed into the wet sludge prior to feeding into the centrifugal sludge thickening unit.