Nowadays we are quite familiar with decanter centrifuges because we can see them almost everywhere in different industry sectors. Many people also think them a very simple machine, they just generate high centrifugal forces which is in turn applied to solids so as to separate them from liquids.
However in real application there are many factors affecting the performance of decanter centrifuges and we have to take into consideration many influences to achieve optimized performance of decanter centrifuges.
We discuss about flocculants application. During the operation of decanter centrifuge we need to use flocculants to speed up the separation of solids from liquids. In field application we encounter the following situation from time to time.
- The centrate has a lot of solids. If this happens the solids concentration in the incoming flow must be checked. For GN Solids Control, its decanter centrifuges are designed to work with highest efficiency when solids concentration is around 20%. If decanter centrifuges are overloaded, they will never work well;
- Differential speed. Three is a slight difference between the rotation speed of centrifugal bowl and auger, usually between a few RPM to less than 20RPM. The lower the differential speed, the longer solids stay in the rotating bowl. There is a very important consideration in this differential speed, the breaking of flocculants, as they intend to break if exposed pressure for long, making them lose the ability to coagulate find particle, and having them discharged with liquid. A trial and error test can determine the optimum differential speed for that particular type of solids;
- Another consideration on flocculants is its strength. When flocculants come into decanter centrifuge, there is a big difference speed between flocculants and the solids. Once flocculants falls on to the wall of rotating wall, there is a huge shearing force exerted on them, and they need to be strong enough to withstand the shearing force to remain as integral particles so as to attract fine particles onto them and move out of decanter centrifuge along with bigger particles.