Used Centrifuges

Centrifuges are used to separate different products or material in a liquid. They separate using centrifugal force, and can separate a liquid from a solid, or two liquids of different densities.

When separating a solid from a liquid, after separation, the solid is referred to as the Cake and the liquid is the Filtrate.

When separating liquids many times the separated liquids will be referred to as phases –eg. light phase, heavy phase.

The terminology varies with each type of product and machine.

The main types of centrifuges are:

• Basket – Top Load Bottom dump
• Basket Peeler
• Basket Screening 
• Basket Top Unload
• Decanter centrifuges
• Disk Bowl Type
• Disc Automatic
• Disc Batch
• Disc Nozzle
• Extractor Counter Current
• Inverting Filter (Heinkel)
• Pusher type
• Peeler type
• Solid Bowl
• Super Centrifuge
•  Laboratory centrifuges

Other terminology that you will hear with reference to centrifuges include:

• Basket Type: Curb, Basket, Plow, wash pipes, Cake detectors
• Disc Bowl: Clarifier, Separator, Auto de-sludger
• Solid Bowl: Housing, Bowl, Scroll, Screw or Conveyor, Drive, Back Drive, Bowl Shape (Contour, Conical, Straight Bowl, Screen Bowl)
• Podbileniak
• Inverting Filter: synonymous with Heinkel
• Pusher or Peeler

The types of centrifuges vary according to the product that has to be separated, and the way the centrifuge discharges after the separation.

Basket Centrifuge

The basket centrifuge is designed for batch type separation of a liquid and a solid. Usually used when you want to retain or collect the solids. After the basket is up to operating speed, the feed is introduced through a feed pipe that is directed toward the basket wall. The centrifugal force evenly distributes the slurry over the side wall. As the liquid passes through the solids, it will then pass through filtration screens, and exits through perforations in the basked side wall. When the solids build to a predetermined thickness, a cake sensing device is triggered to shut off the feed. The basket speed is reduced, and the plow is triggered to remove the solids and discharge out the bottom of the centrifuge.

Clarifier basket centrifuge works in the same manner. However, the basket is solid wall and the liquid decants or flows up and over the lip of the basket where a skimmer tube suctions the liquid. In most cases the basket is covered with a filter bag, making removal of the solids easy. Otherwise, the solids must be manually scooped out.

The basket centrifuge can have a top load feed with bottom discharge, top load feed with manual top unload, solid wall clarifier basket, or perforated basket.

Can be used for chemical, pharmaceutical, food, dewater waste, pigments, crystalline materials.

Decanter solid bowl centrifuge

A decanter is a horizontal solid bowl centrifuge with a taper/conical section at one end for solids discharge. Used for continuous liquid/solid, 2 phase separation primarily for clarification of liquid, Concentration or dewatering of solids, and classification of solid particles. The decanter has an internal conveyor/scroll that rotates in the same direction at a slightly higher speed than the bowl. The product or slurry is feed through a feed pipe to the center cavity of the conveyor where it is evenly dispensed through feed ports into the bowl. As the bowl assembly rotates the centrifugal force allows the suspended solids to settle on the bowl wall where it is conveyed to the taper section for drying before discharged. The clarified liquid is dispensed at the opposite end or larger end of the bowl through weir dams which are adjustable for the liquid pool depth in the bowl. A lower pool depth will provided dryer solids and where a deeper pool will provide wetter solids.

Some decanters can be equipped with centripetal pumps which discharge the clarified liquid under pressure. This also helps to prevent foaming of the effluent. Three phase design are also available.

Decanters can be used for Chemical, Food, Pharmaceutical, and Waste Water Treatment. In applications as fish meal, dewatering potash, dyes, sewage treatment, oil from mud drilling, animal fat for rendering, proteins, restaurant oils for biodiesel, ethanol, wine, beer, fruit juice, animal blood, pulp and paper.

Disc centrifuge

Solids ejecting centrifuge

This centrifuge is a continuous type centrifuge rotating on a vertical axis and can be used for a 2-phase liquid/solid separation or a 3-phase liquid/liquid/solid separation. Usually used when there are fines or soft solids approximately 1% -10% by volume. Separation takes place in the bowl assembly. A stack of discs assist with the sedimentation of the solids as well as splitting light and heavy phase of liquid. The solids collect at the peripheral of the bowl and are discharge either by a time trigger control or sensing device. The timed trigger is known as an intermittently or variable discharge of solids. When full solids capacity is reached a sensor/timer triggers for self-cleaning or automatic discharge to begin. The hydraulic pressure is released which allows the sliding piston in the bowl bottom to drop opening for solids to exit the bowl through the slots around the peripheral of the bowl body. The feed to the centrifuge is continuous and not interrupted. The liquid phases are forced upward and out through a centripetal, paring disc, or open discharge at the top of the bowl.

Can be used for Chemicals, Pharmaceuticals, agricultural chemicals, metal and mineral mining, oil mining and refinery, pulp and paper, waste water treatment, oil, wine, beer, food products, solvents, precious metals.

Solvent, copper, uranium extractions, Dewatering clay. Inorganic and organic chemicals, clarification of liquid, classification of pigments, and separation of liquids, Heavy fuel oil, motor.

Nozzle bowl centrifuge

A continuous disc type centrifuge rotating on a vertical axis can be used as 2-phase or 3-phase separation with higher feed solids concentration of approximately 6-30 % solids by volume. The bowl is designed to slope toward the discharge nozzles. The slurry is feed through the top into center of the bowl. The solids are spun to the side and continuously discharged through nozzles. While the liquid phased are forced up and out of the top of the bowl by means of open discharge, centripetal or paring disc.

This type of centrifuge is usually used for starch, clay, pigments, and yeast.

Solid bowl centrifuge

A solid disc bowl centrifuge is a batch type separation meaning the solid collect in the bowl. The process must be stopped to manually disassemble the bowl for cleaning. Used for separating two liquid phased with minimal solids, less than 1%. Not used for toxic applications due to hazard of manually cleaning.

Used for milk and dairy, vegetable oils, fruit juice,and pharmaceuticals.

Cylinder or Chamber bowl centrifuge

A solid bowl with several cylinders/chambers in side where solids collect on a series of walls as the liquid is forced to follow the channels and discharge through a paring disc at the top of the bowl. Usually used for liquid/solid separation to recover the solids but can be used a liquid/liquid or liquid/liquid/solid separations with minimal to not solids, less than 1% solids.

Can be used for cottage cheese, clarification of beer, wine, fruit juices, cutting oils, varnishes, blood.

Inverting centrifuge

The inverting filter centrifuge is a batch type process used for solid/liquid separations. Has completely sealed process chamber. The basket is lined with a filter cloth. As the basket rotates on a horizontal axis, the product is feed onto the wall of the basket. The liquid drains through the solids and out of the basket through perforations on the wall. Then the product is washed and spun to dewater. The basket speed is reduced and the filter cloth is mechanically pulled out or inverted for the solids to be spun off. When the process is complete the internal process chamber is cleaned with a CIP system. This type of centrifuge is usually used when particle size is precious and can’t be damage by removal; no residual heel is left in the basket.

Used for Pharmaceutical, Agriculture, Fine Chemicals, Special Chemicals, Resins, and Pigments.

Peeler centrifuge

The peeler centrifuge is a batch type centrifuge rotating on a horizontal axis and is used to separate solids from a liquid. Peeler centrifuge is used when solids are to fine for a pusher centrifuge and cannot be dewatered in a basket centrifuge. A feed pipe diverts the slurry toward the basket wall where the centrifugal force forces the liquid to drain through the perforations in the basket wall and the solids remain. When the feed cycle is finished, the cake is washed. Spinning continues for drying. Then the plow/scrapper peels out the solids and is discharged through a chute. Peeler centrifuge can be supplied in a solid basket. In this case the liquid would be siphoned out of the basket.

Used for chemicals, pharmaceuticals, food, and plastics.

Process: Amino acids, antibiotics, antioxidants, bleaches, benzoic acid, benzene, chlorides, fluorides, melamine, potassium bisulphate, sodium perborate, penicillin, resins, sulfur, starch,and sweeteners.

Podbielniak centrifuge

The Podbielniak is a continuous liquid/liquid extracting centrifuge, hermetically sealed rotor, passing soluble liquid from one stream to another by countercurrent flow. Usually used for solvent extraction, chemical washing, separating two liquids with similar densities.

Can be used in Food, Pharmaceuticals, and Chemicals.

Used for lube oil, vaccine, penicillin, erythromycin, tylosin, antibiotics, hormone, vitamin, citrus flavor, edible oil.

Pusher centrifuge

The Pusher centrifuge is a continuous feed type centrifuge on a horizontal axle used to separator course particles from a liquid. The product is feed into the basket area known as the “feed cone”. It is distributed evenly toward the basket wall. The basket is in operation and spinning as the product is feed. The backing plate is spinning at the same speed while pushing in and out to transport the product along the slotted screen where the liquid drains leaving the solids on the screen to be washed, and dried before exiting at the end of the basket. The pusher centrifuge can be equipped with multiple stages. The stages have different diameters, and slot/screen size. Stages help to tumbler the product for washing, and drying.

Used in Chemical, plastics,and foods.

Process: fertilizers, animal feed, boric acid, ascorbic acid, adipic acid, sodium chloride, iron sulphate, sodium sulphate, copper sulphate, sodium bichromate. Ammonium sulphate, potash, urea, calcium nitrate, potassium sulphate. PVC, polystyrene, polyethylene, polypropylene, linters, nitrocellulose. Extraction residues, meat pulp, rock phosphate, gypsum, ores, coal.

Tubular Super Centrifuge

Sharples/Alfa Laval manufacture hi-speed vertical tubular bowl centrifuge units that spin at 15000 RPM. For batch type process, this centrifuge was designed for clarifier, 2 phase liquid/liquid, liquid/solids having very low solids content, or separator, 3 phase liquid/liquid/solids again having very low solids. The bowl is suspended from a spindle shaft that couples to the neck of the bowl. The bowl bottom neck floats in the drag assembly inside a bronze bushing. The bowl is driven by an electric motor 2-5 hp depending on the size and model. The centrifuge bowl is brought up to speed. Then the feed is introduced through a feed nozzle into the bottom of the bowl. As the product is separated the solids are slung to the side wall while the liquid phases are force upward and out discharge ports in the top of the bowl and into the cover assembly for distribution. At the end of the cycle, the bowl is disassembled to removes solids and clean. In some cases a Three-wing is inserted into the bowl and is held into place by tension springs. The three-wing help channel the liquid phases out of the bowl.

Used in Chemical, Food, Pharmaceutical.

Commonly used for blood and plasma, vegetable oil and water, Hydraulic, Diesel fuel, Diesel lubricating, heavy fuel, Turbine lubricating, Transformer, Cutting and Grinding oils, and Printing ink.