ANDRITZ Separation - ANDRITZ Group

- Model SZ - Pusher Centrifuge

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Our pusher centrifuge ensures maximum online availability with minimum maintenance and low space requirement in many solid/liquid separation processes.

In continuous solid/liquid separation, Krauss-Maffei pusher centrifuges combine high availability with minimum maintenance and reduced specific space requirement. They enable effective dewatering of fast filtering products at high throughput rates. The quality of the final product can be increased using a variety of washing modes. Krauss-Maffei pusher centrifuges are applied in many fields of industry. Examples of these applications are found in bulk chemicals treatment, plastics production, mining and minerals processing, the fiber industry, and in food processing. ANDRITZ KMPT boasts over 80 years of experience with Krauss-Maffei centrifuges in over 5,000 installations across the globe.

Low energy consumption

  • More than 25% in energy savings compared to competitors due to optimized design of process area and efficient pusher system

Outstanding product quality

  • Highly efficient cake washing modes.
  • Minimum particle breakage with optimized feed system.
  • Selection of screen configurations designed for your product parameters to minimize product loss and maximize dewatering properties

Unmatched capacity

Superior maintenance concept

  • Innovative, patented ANDRITZ KMPT cartridge system ensures minimum production downtime
  • Optimized wear parts ensure fast replacement
  • Extended lifetime of screens due to efficient pre-accelerating feed distributor

Chemicals:

Soda ash. petrochemicals, and polymers (ABS, adipic acid, POM, paraxylene), base chemicals (soda, chlorides, borax, sodium chlorate, sulfates, lithium compounds), agrochemicals (ammonium sulfate, potash compounds, chlorides, sulfates), specialty chemicals, and chemical recovery

Food:

Neutraceuticals and functional ingredients (baking soda), table salt, industrial fermentation (lysine), and animal processing

Mining and Minerals:

Potash and potassium compounds, phosphate, flue gas desulfurization (FGD), salt, and metal refining (lithium compounds)

  • Average particle size 80 - 2000 µm
  • Feed solids concentration > 20% by wt. (crystalline products)
  • Solids throughput up to 150 t/h
  • Basket diameter 250 - 1250 mm
  • Solids recovery up to 99% by wt.



Krauss-Maffei pusher centrifuges run in continuous operation. The product is fed through a feed pipe (or feed screw in the case of products that do not flow freely) into the feed distributor, which rotates with the basket. This accelerates the slurry and feeds it with uniform distribution to the feed zone, where the greater part of the liquid (approx. 80%) is filtered. In the feed zone, the solids form a stable filter cake ring. The filter cake is conveyed in the direction of the solids discharge stroke by stroke due to the relative axial movement between pusher bottom and screen basket. During this process, an intact filter cake forms over the entire length of the screen. As the filter cake progresses from the feed zone to the solids discharge, it can be washed, as required. For this purpose wash liquor is applied to the cake surface, displacing the suspension liquid and any impurities. Multi-stage washing is also possible, with several successive washing zones. Multi-stage centrifuges with several baskets loosen the filter cake and reshape it by moving it from the inner basket to the next larger basket. As a result of this re-shaping process, moisture that collects between the particles is exposed and filtered. The solids are discharged at the end of the basket after each pusher movement.

Feed conditions
In order to optimize the machine size and achieve maximum operating reliability, it is important to provide uniform and concentrated slurry feed. As the upstream equipment, such as crystallizers or reactors, frequently do not meet these requirements satisfactorily, a pre-thickener system is usually applied. This system evens out fluctuations in the feed conditions and minimizes the hydraulic load of the centrifuge. As a result a smaller machine size is often selected. Stationary or dynamic units have become established as pre-thickeners, depending on the type of application. Examples of stationary equipment are sedimentation tanks and thickener filters, while possible dynamic equipment includes curved screens, hydrocyclones, vibration screens, and EC screen thickeners. In stationary thickeners, a metering unit is required to control the feed to the centrifuge, and in dynamic thickeners, the feed to the thickener must be monitored.

Alternatively, an integrated pre-thickening stage can be offered, which makes the machine less sensitive to changes in feed conditions and opens up a wider field of applications.

Feeding
The feed system has the most significant impact on operation of the centrifuge. Uniform distribution of the slurry is the basic requirement for trouble-free operation of the centrifuge.

Vane-type feed distributor

A special feature of Krauss-Maffei pusher centrifuges is the vane-type feed distributor. The slurry flow is diverted in the direction of rotation of the basket by the vane-type feed distributor. The slurry is pre-accelerated to such an extent that the difference between the speed of the slurry and the screen is practically zero. In this way, particle attrition is noticeably reduced in comparison with other feed systems. This results in more uniform formation of the filter cake and higher throughput rates. The machine is filled evenly and runs much more smoothly and quietly as a result. Benefits are obtained from reduced maintenance costs as a result of low wear.

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