Alfa Laval – decanter centrifuge technology

1 alfa Laval in brief alfa Laval is a leading global provider of specialized products and engineered solutions. Our equipment, systems and services are dedicated to helping customers to optimize the performance of their processes. Time and time again. We help our customers to heat, cool, separate and transport products such as oil, water, chemicals, beverages, foodstuff, starch and pharmaceuticals. Our worldwide organization works closely with customers in almost 100 countries alfa Laval decanter centrifuge technology to help them stay ahead. Separating solids from liquids How to contact alfa Laval Up-to-date alfa Laval contact details for all countries are always available on our website at PCD00002EN 0909.

2 Separating solids from liquids plays a key role in countless industrial processes. decanter centrifuges from alfa Laval perform this crucial function exceptionally well. Working principles VFD-controlled motor for screw conveyor Pond of clarified liquid Outlet for clarified liquid Screw conveyor Continuous separation Accelerating the process centre line. Rotating this unit rapidly Virtually all branches of industry need However, such clarification is an means that the effect of gravity is to separate solids from liquids at some extremely slow process and was not replaced by a centrifugal force the point in their manufacturing processes.

3 Able to meet industry's needs for more effect of which can be up to 4000. alfa Laval has more than fifty years of rapid, controllable results. times greater. experience in meeting this requirement The idea behind the development of using decanter centrifuge technology . the decanter centrifuge was therefore This force is then used to separate The decanter centrifuge is based on to provide the continuous mechanical solids from liquids efficiently in a the simple idea of a clarifier or settling separation of liquids from solids, to manner that is easy to control. tank, in which particles, sediment and keep pace with modern industrial Depending on the particular solids gradually fall to the bottom due demands.

4 Configuration and surrounding to the force of gravity. equipment, a decanter centrifuge can In essence, a centrifuge is a clarifier be used to separate a wide range of whose base is wrapped around a different solids from one or two liquid phases, on a continuous basis. 4 alfa Laval decanter centrifuge technology Surface area Feed system Cake removal Weirs Side wall Cake depth compaction Clarifier becomes a decanter centrifuge Inlet tube Erosion-protected Solids deposited on solids discharge ports bowl wall Main motor Conical beach section How a decanter centrifuge works The sediment formed by the solid The speed of the screw conveyor may A decanter centrifuge separates solids particles is continuously removed by be automatically adjusted by use of the from one or two liquid phases in one the screw conveyor, which rotates at a variable frequency drive (VFD)

5 In order single continuous process. This is done different speed than the bowl. As a to adjust to variation in the solids load. using centrifugal forces that can be result, the solids are gradually well beyond 3000 times greater than ploughed out of the pond and up the gravity. conical beach . When subject to such forces, the The centrifugal force compacts the denser solid particles are pressed solids and expels the surplus liquid. outwards against the rotating bowl The dried solids then discharge from wall, while the less dense liquid phase the bowl. The clarified liquid phase or forms a concentric inner layer. Different phases overflow the dam plates dam plates are used to vary the depth situated at the opposite end of the of the liquid the so-called pond as bowl.

6 Baffles within the centrifuge required. casing direct the separated phases into the correct flow path and prevent any risk of cross-contamination. alfa Laval decanter centrifuge technology 5. The key to exceptional performance Wide-ranging performance alfa Laval decanter centrifuges provide exceptional performance when separating solids from liquids, and make it possible to do so continuously, efficiently and controllably. Decanters are invariably the first choice to meet such separation needs by virtue of their high reliability, continuous operation, low capital cost/capacity ratio and low maintenance costs. alfa Laval decanter centrifuges are designed to handle a wide range of solid particles with diameters from 5.

7 Mm to a few microns. decanter units can also handle slurries with a solid content from as low as w/w to more than 65% w/w. decanter centrifuges can accept variations in the feed more effectively than other types of centrifuge or separation equipment. Performance criteria Five crucial factors determine the In specifying a decanter centrifuge for a The four main sections performance of decanter centrifuges: particular application, a series of other alfa Laval decanter centrifuges feature the centrifugal force required for specific design considerations has to four main sections, each optimized for sedimentation of the solids be taken into account: maximum performance.

8 The clarification area necessary to the pitch of the conveyor capture the solids feed zone design Inlet zone the differential speed required to beach angle The inlet zone accelerates the feed transport the solids out of the bowl surface slurry up to the speed of the bowl. A. decanter abrasion resistance properly designed inlet zone keeps any the hydrodynamic design, which materials used in construction. degradation of the feed solids to a determines the exact parameters for minimum as well as avoiding disturb- the turbulence ance of the sediment in the bowl. the design of the conveyor and beach sections, which are important for efficient solids transportation.

9 6 alfa Laval decanter centrifuge technology A number of feed zone specifications Solids discharge section Liquid discharge section are available for alfa Laval decanter Depending on the application, the In a two-phase decanter , the liquid centrifuges, each designed to ensure consistency of the separated solids level is regulated by dam plates. maximum performance in conjunction can vary from a dry powder to a paste. When operating in a three-phase with a specific process. The configuration of the discharge mode, each phase discharges over a zone is therefore chosen to enable set of dam plates into separate baffled Screw conveyor such cakes to exit as effectively as compartments in the casing.

10 The key to good decanter performance possible. In certain applications, a centripetal lies in the efficient, effective scrolling of pump discharge that utilizes the the sedimented solids. The design of Innovative alfa Laval design enables pressure head developed by the the screw conveyor is therefore crucial. erosion-prone components used in the rotating liquid phase is used to pump solids discharge zone to be replaced the liquid from the decanter . alfa Laval has the expertise needed to on site at low cost and with a minimum match the demands involved in specific of disturbance to production. industrial processes with specific configurations of flight pitch, lead angle and differential speed, in order to secure the best possible results.