Centrifugal separation
The need to separate different liquid phases and solids from each other is part of practically every industrial process. Alfa Laval has more than one hundred and twenty years of experience in meeting this requirement using either decanter or disc stack centrifuge technology, and our products perform this crucial function exceptionally well.
The product range is based on disc stack centrifuges and decanter centrifuges for separating liquids from each other or for removing solid particles from liquids. These products are used for many different functions in the food and other process industries, on board ships to purify fuel and lubricating oil, on oil platforms to separate oil and water, in manufacturing industry to clean industrial fluids, and for industrial and municipal sewage treatment.
Decanter centrifuges
Separating solids from liquids plays a key role in countless industrial, food and treatment processes. Decanter centrifuges from Alfa Laval perform this crucial function exceptionally well.
The basic physics behind the decanter is the natural settling action that gravity forces on suspended solids. Nevertheless, waiting for nature to do its job often takes too long.
Matching customer needs
Alfa Laval has become the market leader in decanter centrifuge technology. Our know-how and specialist process experience put us in a unique position to match the exact needs of each customer for each particular application and installation.
With different design, lengths and cone geometries, our range of decanters can be applied in any processing environment that requires a separation step between solids and liquids. Alfa Laval decanter centrifuges provide meticulous control, low cost and high reliability.
Centrifuge systems - modules
Decanter technology from Alfa Laval can be applied to many processes that require solids separation from liquids and in many cases a decanter system can be the most cost effective solution.
By combining our core competencies within separation, centrifuge systems have been developed with a plug and play attribute. This gives the advantage of lower lead times and easier installation procedures when capacity extensions or additional lines become necessary.
Decanter centrifuge systems such as the ALSYS 400 for dewatering sludge, the LYNX 40 for drilling mud and others have been proven in the field again and again as a standard solution to different oil solid separation requirements. Other centrifuge systems have also been developed for protein recovery and other product recovery duties.
Stand alone units
With the widest range of decanter centrifuges that are equipped with leading edge technology and the highest standards in design and manufacturing, Alfa Laval decanter centrifuges are the clear leader.
Our range consists of several bowl diameters, of which some sizes are available with different design, lengths and cone geometries. Alfa Laval has perfected the decanter to separate solids from liquids, liquids from liquids and a mixture of all three phases.
Disc stack centrifuges
With a clarifier or settling tank, particles and liquid phases, will fall to the bottom, but the lack of control and the length of time required makes natural settling unsuitable for modern industrial processes.
In essence, a disc stack centrifuge is a clarifier whose base is wrapped around a centre line. Rotating this unit rapidly means that the effect of gravity is replaced by a controllable centrifugal force – the effect of which can be more than 10 000 times greater than gravity on solids suspended in liquids. When subject to such forces, the denser solid particles are pressed outwards against the rotating bowl wall, while the less dense liquid phases form concentric inner layers.
The disc stack
The key to good separation performance lies in the efficiency of the disc stack, the heart of the centrifuge, therefore the design of the disc is crucial. Alfa Laval has the expertise needed to match the demands involved in specific industrial processes.
2-Phase 3-Phase
Depending on the separation requirements disc stack centrifuges can handle solids in three different ways, from liquid/liquid separation (both 2-phase or 3-phase applications) to the separation of slurries having a solids content approaching 30% (normally 2-phase applications).
Nozzle bowl centrifuges
Many liquid processes contain relatively high levels of solid content and when high throughputs are required with solids content of more than 10% the continuous discharge effect created by nozzles in the periphery of the bowl is put to use.
The Nozzle bowl centrifuge is most often used for classification of solids according to size, dewatering and washing of solids, and for clarification of liquids containing relatively high concentrations of solids. It can also be used for 3 phase applications where two liquid phases and a solids phase need to be separated in one step.
If the concentration of the solids varies over time a recirculation system can be added to the design of the centrifuge in order to gain greater control over the separation procedure.
Solid wall bowl centrifuges
The solid wall bowl centrifuge is designed to retain solids within the disc stack centrifuge and is closest to the original cream separator developed by De Laval.
The solid wall bowl centrifuge is often used in processes that require liquid/liquid or liquid/solids separation when the solids content in the feed is no more than about 1% by volume. Because of the simplicity of the design, very high g-values can be obtained and this centrifuge is thus very efficient in the recovery of fine particles.
Self cleaning bowl
Many processes require solids to be discharged intermittently during operation, or for processes with liquids containing higher solids content (up to approx. 10%) the intermittent solids discharge centrifuge is an ideal solution.
Designed with a unique hydraulic system below the separation space in the bowl which forces the sliding bowl bottom to drop down, thus opening the solids ports at the bowl periphery at preset intervals. This provides what is known as a self cleaning effect when the solids are removed all at once during operation.
This design has vast applications in all industries and is one of the most common types of disc stack centrifuge for Alfa Laval.
