Solid bowl and screen bowl decanter centrifuges
The two primary types of decanter centrifuge are solid bowl decanters and screen bowl decanters.
Solid bowl decanter centrifuge, used to process PVC slurry
900mm screen bowl decanter, with casing top removed
- simple to use
- low operating costs
- low maintenance costs
- compact footprint
- low cake moisture
- high solids removal
- high centrate clarity
- long operational life
- user-friendly, advanced control technology
- screen and solid bowl configurations
- bowl diameter sizes from 150mm – 1400mm
- sealed and pressure-tight options
- state-of-the-art, abrasion-resistant materials appropriate to application
- for slurries 1-70% solids: particles 1 micron – 1cm
- solids output from 0.1 – 100t/h dry solids
- centrate output from 40 L/min to 3,500 L/min
- CE, EN12547 and ISO9001-2008-compliant
- Meets environmental noise regulations
Solid bowl decanter centrifuges
The commonest form of decanter is the solid bowl decanter. It is used in to dewater slurries in many process applications, such as:
- Effluent treatment
- PTA, PVC and polyolefins
- MMA and ABS
- HDPE and styrene
- gypsum dewatering
We offer an extensive range of sizes, capacities and materials of construction (the size range table below gives more detailed information). We also manufacture fume-tight and pressure decanters for specialist and hazardous applications.
Screen bowl decanter centrifuges
The screen bowl decanter centrifuge is operationally similar to the solid bowl units, but provides greater washing efficiency and enhanced moisture removal in applications involving crystalline materials. The screen bowl decanter operates in two stages, combining the clarification and sedimentation advantages of the solid bowl centrifuge and the dewatering benefits of an additional screen section. These centrifuges are typically used for processing BPA, PX, some minerals and polyolefins.
- mother liquor and wash liquor can be collected separately
- performance less affected by feed consistency variations
- low moistures (due to final drainage of the cake through the screen)
- cake-washing facility
- segregates wash and mother liquors
- fine screen slots limit solids losses
Would you like to assess the results achievable with a decanter centrifuge? Find out more in our Process laboratory section
Decanter centrifuges: principles of operation
The fundamental principle of a decanter centrifuge is the acceleration of sedimentation under gravity. Diagram (a) below shows a simple settling tank with a continuously moving scraper removing the settled solids at the left-hand end. The liquid flows over the scraper blades and leaves the tank at the right-hand end. According to Stokes’ Law, the rate at which a solid particle within the tank will settle depends on a number of factors including the relative density of the solids and the liquid, the size of the particle and the acceleration due to gravity.
If the tank is transformed, as shown in Diagram (b) into a tapered cylinder (c) and the cylinder is rotated at high speed about its centre line, a high centrifugal g-force is exerted on the liquid and solids. This centrifugal g-force replaces the acceleration due to gravity in Stokes’ Law and results in rapid sedimentation of those particles of greater density than the liquid. The continuously moving scraper in (a) is replaced by the helix shown in (c), which transports the solids out of the tapered end of the cylinder allowing continuous separation. The original settling tank (a) has now been transformed into a decanting centrifuge (c).
There are many variations of decanting centrifuges in use in a wide variety of process applications: however the basic principles outlined above apply to all decanter centrifuges.
Broadbent decanter centrifuge designs are available with capacities up to 200m3 / hour of feed and provide:
- excellent process performance
- proven heavy duty reliable designs
- continuous operation with minimum operator supervision
- long operational life
- sealed or pressure-tight options available for use with hazardous chemicals
- fully wear-protected for use with abrasive minerals
available in a wide range of materials of construction.