A laboratory tabletop centrifuge. The rotating unit, called the rotor, has fixed holes drilled at an angle (to the vertical), visible inside the smooth silver rim. Sample tubes are placed in these slots and the motor is spun. As the centrifugal force is in the horizontal plane and the tubes are fixed at an angle, the particles have to travel only a short distance before they hit the wall of the tube and then slide down to the bottom. These angle rotors are very popular in the lab for routine use.
In which industrial process you will use centrifugal separator? Report Abuse. Are you sure that you want to delete this answer? Oil purifier in Power plant,Sugar mill,Edible oil food Industries,different process in Chemical Manufacturer Industries.& Laboratories.Etc. Ricky414 6 years ago. You have to come up with a basic framework and ask some specific questions to get meaningful answers. Don't expect others to do your projects.
A centrifuge is a piece of equipment that puts an object in rotation around a fixed axis (spins it in a circle), applying a force perpendicular to the axis of spin (outward) that can be very strong. The centrifuge works using the sedimentation principle, where the centrifugal acceleration causes denser substances and particles to move outward in the radial direction. At the same time, objects that are less dense are displaced and move to the center. In a laboratory centrifuge that uses sample tubes, the radial acceleration causes denser particles to settle to the bottom of the tube, while low-density substances rise to the top.[1]
There are three types of centrifuge designed for different applications. Industrial scale centrifuges are commonly used in manufacturing and waste processing to sediment suspended solids, or to separate immiscible liquids. An example is the cream separator found in dairies. Very high speed centrifuges and ultracentrifuges able to provide very high accelerations can separate fine particles down to the nano-scale, and molecules of different masses.
Large centrifuges are used to simulate high gravity or acceleration environments (for example, high-G training for test pilots). Medium-sized centrifuges are used in washing machines and at some swimming pools to wring water out of fabrics.
Gas centrifuges are used for isotope separation, such as to enrich nuclear fuel for fissile isotopes.
- 3Uses
History[edit]
English military engineer Benjamin Robins (1707–1751) invented a whirling arm apparatus to determine drag. In 1864, Antonin Prandtl proposed the idea of a dairy centrifuge to separate cream from milk. The idea was subsequently put into practice by his brother, Alexander Prandtl, who made improvements to his brother's design, and exhibited a working butterfat extraction machine in 1875.[2]
Types[edit]
Whole blood is often separated, using a centrifuge, into components for storage and transportation
A centrifuge machine can be described as a machine with a rapidly rotating container that applies centrifugal force to its contents. There are multiple types of centrifuge, which can be classified by intended use or by rotor design:
Types by rotor design:[3][4][5][6]
- Fixed-angle centrifuges are designed to hold the sample containers at a constant angle relative to the central axis.
- Swinging head (or swinging bucket) centrifuges, in contrast to fixed-angle centrifuges, have a hinge where the sample containers are attached to the central rotor. This allows all of the samples to swing outwards as the centrifuge is spun.
- Continuous tubular centrifuges do not have individual sample vessels and are used for high volume applications.
Types by intended use:
- Laboratory centrifuges, are general-purpose instruments of several types with distinct, but overlapping, capabilities. These include clinical centrifuges, superspeed centrifuges and preparative ultracentrifuges.
- Analytical ultracentrifuges are designed to perform sedimentation analysis of macromolecules using the principles devised by Theodor Svedberg.
- Haematocrit centrifuges are used to measure the volume percentage of red blood cells in whole blood.
- Gas centrifuges, including Zippe-type centrifuges, for isotopic separations in the gas phase.
Industrial centrifuges may otherwise be classified according to the type of separation of the high density fraction from the low density one.
Generally, there are two types of centrifuges: the filtration and sedimentation centrifuges. For the filtration or the so-called screen centrifuge the drum is perforated and is inserted with a filter, for example a filter cloth, wire mesh or lot screen. The suspension flows through the filter and the drum with the perforated wall from the inside to the outside. In this way the solid material is restrained and can be removed. The kind of removing depends on the type of centrifuge, for example manually or periodically. Common types are:
- Screen/scroll centrifuges (Screen centrifuges, where the centrifugal acceleration allows the liquid to pass through a screen of some sort, through which the solids cannot go (due to granulometry larger than the screen gap or due to agglomeration))
- Inverting filter centrifuges
- Sliding discharge centrifuges
- Pendulum centrifuges
In the sedimentation centrifuges the drum is a solid wall (not perforated). This type of centrifuge is used for the purification of a suspension. For the acceleration of the natural deposition process of suspension the centrifuges use centrifugal force. With so-called overflow centrifuges the suspension is drained off and the liquid is added constantly.Common types are:[7]
- Pendulum centrifuges
- Separator centrifuges (Continuous liquid); common types are:
- Tubular centrifuges
- Decanter centrifuges, in which there is no physical separation between the solid and liquid phase, rather an accelerated settling due to centrifugal acceleration.
Though most modern centrifuges are electrically powered, a hand-powered variant inspired by the whirligig has been developed for medical applications in developing countries.[8]
Uses[edit]
Samples placed in a small laboratory centrifuge
Laboratory separations[edit]
A wide variety of laboratory-scale centrifuges are used in chemistry, biology, biochemistry and clinical medicine for isolating and separating suspensions and immiscible liquids. They vary widely in speed, capacity, temperature control, and other characteristics. Laboratory centrifuges often can accept a range of different fixed-angle and swinging bucket rotors able to carry different numbers of centrifuge tubes and rated for specific maximum speeds. Controls vary from simple electrical timers to programmable models able to control acceleration and deceleration rates, running speeds, and temperature regimes. Ultracentrifuges spin the rotors under vacuum, eliminating air resistance and enabling exact temperature control. Zonal rotors and continuous flow systems are capable of handing bulk and larger sample volumes, respectively, in a laboratory-scale instrument.[1]Another application in laboratories is blood separation. Blood separates into cells and proteins (RBC,WBC, platelets, etc.) and serum.DNA preparation is another common application for pharmacogenetics and clinical diagnosis. DNA samples are purified and the DNA is prepped for separation by adding buffers and then centrifuging it for a certain amount of time. The blood waste is then removed and another buffer is added and spun inside the centrifuge again. Once the blood waste is removed and another buffer is added the pellet can be suspended and cooled. Proteins can then be removed and the entire thing can be centrifuged again and the DNA can be isolated completely.
Isotope separation[edit]
Other centrifuges, the first being the Zippe-type centrifuge, separate isotopes,[9] and these kinds of centrifuges are in use in nuclear power and nuclear weapon programs.
Aeronautics and astronautics[edit]
The 20 g centrifuge at the NASA Ames Research Center
Human centrifuges are exceptionally large centrifuges that test the reactions and tolerance of pilots and astronauts to acceleration above those experienced in the Earth's gravity.
The first centrifuges used for human research were used by Erasmus Darwin, the grandfather of Charles Darwin. The first largescale human centrifuge designed for Aeronautical training was created in Germany in 1933.[10]
The US Air Force at Brooks City Base, Texas operates a human centrifuge while awaiting completion of the new human centrifuge in construction at Wright-Patterson AFB, Ohio. The centrifuge at Brooks City Base is operated by the United States Air Force School of Aerospace Medicine for the purpose of training and evaluating prospective fighter pilots for high-g flight in Air Force fighter aircraft.[11]
The use of large centrifuges to simulate a feeling of gravity has been proposed for future long-duration space missions. Exposure to this simulated gravity would prevent or reduce the bone decalcification and muscle atrophy that affect individuals exposed to long periods of freefall.[11][12]
Non-Human centrifuge
At the European Space Agency (ESA) technology center ESTEC (in Noordwijk, the Netherlands) an 8-meter diameter centrifuge is used to expose samples in both fields of Life Sciences as well as Physical Sciences. This Large Diameter Centrifuge (LDC)[13] is operational since 2007. Samples can be exposed to a maximum of 20 times Earth gravity. With its four arms and six freely swing out gondolas it is possible to expose samples with different g-levels at the same time. Gondolas can be fixed at eight different position. Depending on their locations one could e.g. run an experiment at 5 and 10g in the same run. Each gondola can hold an experiment of maximum 80 kg. Experiments performed in this facility ranged from zebra fish, metal alloys, plasma,[14] cells,[15] liquids, Planaria,[16] Drosophila[17] or plants
Industrial centrifugal separator[edit]
Industrial centrifugal separator is a coolant filtration system for separating particles from liquid like, grinding machining coolant. It is usually used for non-ferrous particles separation such as, silicon, glass, ceramic, and graphite etc. The filtering process does not require any consumption parts like filter bags, which saves the earth from harm.[18][19]
Geotechnical centrifuge modeling[edit]
Geotechnical centrifuge modeling is used for physical testing of models involving soils. Centrifuge acceleration is applied to scale models to scale the gravitational acceleration and enable prototype scale stresses to be obtained in scale models. Problems such as building and bridge foundations, earth dams, tunnels, and slope stability, including effects such as blast loading and earthquake shaking.[20]
Synthesis of materials[edit]
High gravity conditions generated by centrifuge are applied in the chemical industry, casting, and material synthesis.[21][22][23][24] The convection and mass transfer are greatly affected by the gravitational condition. Researchers reported that the high-gravity level can effectively affect the phase composition and morphology of the products.[21]
Commercial applications[edit]
Sugar centrifugal machines for separating sugar crystals, retrieved on June 5, 2010
- Standalone centrifuges for drying (hand-washed) clothes – usually with a water outlet.
- Washing machines are designed to act as centrifuges to get rid of excess water in laundry loads.
- Centrifuges are used in the attraction Mission: SPACE, located at Epcot in Walt Disney World, which propels riders using a combination of a centrifuge and a motion simulator to simulate the feeling of going into space.
- In soil mechanics, centrifuges utilize centrifugal acceleration to match soil stresses in a scale model to those found in reality.
- Large industrial centrifuges are commonly used in water and wastewater treatment to dry sludges. The resulting dry product is often termed cake, and the water leaving a centrifuge after most of the solids have been removed is called centrate.
- Large industrial centrifuges are also used in the oil industry to remove solids from the drilling fluid.
- Disc-stack centrifuges used by some companies in the oil sands industry to separate small amounts of water and solids from bitumen
- Centrifuges are used to separate cream (remove fat) from milk; see Separator (milk).
Mathematical description[edit]
Protocols for centrifugation typically specify the amount of acceleration to be applied to the sample, rather than specifying a rotational speed such as revolutions per minute. This distinction is important because two rotors with different diameters running at the same rotational speed will subject samples to different accelerations. During circular motion the acceleration is the product of the radius and the square of the angular velocity, and the acceleration relative to 'g' is traditionally named 'relative centrifugal force' (RCF). The acceleration is measured in multiples of 'g' (or × 'g'), the standard acceleration due to gravity at the Earth's surface, a dimensionless quantity given by the expression:
A 19th-century hand cranked laboratory centrifuge.
where
- is earth's gravitational acceleration,
- is the rotational radius,
- is the angular velocity in radians per unit time
This relationship may be written as
or
where
- is the rotational radius measured in millimeters (mm), and
- is rotational speed measured in revolutions per minute (RPM).
To avoid having to perform a mathematical calculation every time, one can find nomograms for converting RCF to rpm for a rotor of a given radius. A ruler or other straight edge lined up with the radius on one scale, and the desired RCF on another scale, will point at the correct rpm on the third scale.[25] Based on automatic rotor recognition, modern centrifuges have a button for automatic conversion from RCF to rpm and vice versa.
See also[edit]
- Separation process—includes list of techniques
References and notes[edit]
- ^ abSusan R. Mikkelsen & Eduardo Cortón. Bioanalytical Chemistry, Ch. 13. Centrifugation Methods. John Wiley & Sons, Mar 4, 2004, pp. 247–267.
- ^Vogel-Prandtl, Johanna Ludwig Prandtl: A Biographical Sketch, Remembrances and Documents, English trans. V. Vasanta Ram. The International Centre for Theoretical Physics Trieste, Italy, pub. August 14, 2004. pp. 10–11.
- ^'Basics of Centrifugation'. Cole-Parmer. Retrieved 11 March 2012.
- ^'Plasmid DNA Separation: Fixed-Angle and Vertical Rotors in the Thermo Scientific Sorvall Discovery™ M120 & M150 Microultracentrifuges' (Thermo Fischer publication)
- ^http://uqu.edu.sa/files2/tiny_mce/plugins/filemanager/files/4250119/lectures/1._instr.pdf
- ^Heidcamp, Dr. William H. 'Appendix F'. Cell Biology Laboratory Manual. Gustavus Adolphus College. Retrieved 11 March 2012.
- ^'Centrifuges'.
- ^M. Saad Bhamla, Brandon Benson, Chew Chai, Georgios Katsikis, Aanchal Johri & Manu Prakash (10 January 2017). 'Hand-powered ultralow-cost paper centrifuge'. Nature. 1: 0009. doi:10.1038/s41551-016-0009.CS1 maint: uses authors parameter (link)
- ^Cordesman, Anthony H.; Al-Rodhan, Khalid R. (2006). Iran's Weapons of Mass Destruction: The Real and Potential Threat. CSIS. ISBN9780892064854.
- ^http://www.dtic.mil/dtic/tr/fulltext/u2/a236267.pdf
- ^ ab'The Pull of HyperGravity – A NASA researcher is studying the strange effects of artificial gravity on humans'. NASA. Retrieved 11 March 2012.
- ^Hsu, Jeremy. 'New Artificial Gravity Tests in Space Could Help Astronauts'. Space.com. Retrieved 11 March 2012.
- ^van Loon JJWA, Krause J., Cunha H., Goncalves J., Almeida H., Schiller P. The Large Diameter Centrifuge, LDC, for life and physical sciences and technology. Proc. of the 'Life in Space for Life on Earth Symposium', Angers, France, 22–27 June 2008. ESA SP-663, December 2008.
- ^Šperka, Jiří; Souček, Pavel; Loon, Jack J. W. A. Van; Dowson, Alan; Schwarz, Christian; Krause, Jutta; Kroesen, Gerrit; Kudrle, Vít (2013-12-01). 'Hypergravity effects on glide arc plasma'. The European Physical Journal D. 67 (12): 261. Bibcode:2013EPJD...67..261S. doi:10.1140/epjd/e2013-40408-7. ISSN1434-6060.
- ^Szulcek, Robert; Bezu, Jan van; Boonstra, Johannes; Loon, Jack J. W. A. van; Amerongen, Geerten P. van Nieuw (2015-12-04). 'Transient Intervals of Hyper-Gravity Enhance Endothelial Barrier Integrity: Impact of Mechanical and Gravitational Forces Measured Electrically'. PLOS One. 10 (12): e0144269. Bibcode:2015PLoSO..1044269S. doi:10.1371/journal.pone.0144269. ISSN1932-6203. PMC4670102. PMID26637177.
- ^Adell, Teresa; Saló, Emili; Loon, Jack J. W. A. van; Auletta, Gennaro (2014-09-17). 'Planarians Sense Simulated Microgravity and Hypergravity'. BioMed Research International. 2014: 679672. doi:10.1155/2014/679672. ISSN2314-6133. PMC4182696. PMID25309918.
- ^Paloma Serrano, Jack J.W. A. van Loon, F. Javier Medina · Ra´ ul Herranz Relation between motility accelerated aging and gene expression in selected Drosophila strains under hypergravity conditions. Microgravity Sci. Technol. (2013) 25:67–72. DOI 10.1007/s12217-012-9334-5.
- ^'What is an Industrial Centrifuge? An industrial centrifuge is a machine used for fluid/particle sep'. KYTE. Retrieved 21 September 2017.
- ^'Chip Removal Centrifugal Machine'. Chinminn. Retrieved 21 September 2017.
- ^C. W. W. Ng; Y. H. Wang; L. M. Zhang (2006). Physical Modelling in Geotechnics: proceedings of the Sixth International Conference on Physical Modelling in Geotechnics. Taylor & Francis. p. 135. ISBN978-0-415-41586-6.
- ^ abYin, Xi; Chen, Kexin; Zhou, Heping; Ning, Xiaoshan (August 2010). 'Combustion Synthesis of Ti3SiC2/TiC Composites from Elemental Powders under High-Gravity Conditions'. Journal of the American Ceramic Society. 93 (8): 2182–2187. doi:10.1111/j.1551-2916.2010.03714.x.
- ^Mesquita, R.A.; Leiva, D.R.; Yavari, A.R.; Botta Filho, W.J. (April 2007). 'Microstructures and mechanical properties of bulk AlFeNd(Cu,Si) alloys obtained through centrifugal force casting'. Materials Science and Engineering: A. 452–453: 161–169. doi:10.1016/j.msea.2006.10.082.
- ^Chen, Jian-Feng; Wang, Yu-Hong; Guo, Fen; Wang, Xin-Ming; Zheng, Chong (April 2000). 'Synthesis of Nanoparticles with Novel Technology: High-Gravity Reactive Precipitation'. Industrial & Engineering Chemistry Research. 39 (4): 948–954. doi:10.1021/ie990549a.
- ^Abe, Yoshiyuki; Maizza, Giovanni; Bellingeri, Stefano; Ishizuka, Masao; Nagasaka, Yuji; Suzuki, Tetsuya (January 2001). 'Diamond synthesis by high-gravity d.c. plasma cvd (hgcvd) with active control of the substrate temperature'. Acta Astronautica. 48 (2–3): 121–127. Bibcode:2001AcAau..48..121A. doi:10.1016/S0094-5765(00)00149-1.
- ^Nomogram exampleArchived December 9, 2013, at the Wayback Machine
Further reading[edit]
External links[edit]
Wikimedia Commons has media related to Centrifuges. |
Look up centrifuge in Wiktionary, the free dictionary. |
- Selection of historical centrifuges in the Virtual Laboratory of the Max Planck Institute for the History of Science
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A centrifugal water–oil separator, centrifugal oil–water separator or centrifugal liquid–liquid separator is a device designed to separate oil and water by centrifugation. It generally contains a cylindrical container that rotates inside a larger stationary container. The denser liquid, usually water, accumulates at the periphery of the rotating container and is collected from the side of the device, whereas the less dense liquid, usually oil, accumulates at the rotation axis and is collected from the centre.[1]
Centrifugal oil–water separators are used for waste water processing and for cleanup of oil spills on sea or on lake.[2]
Centrifugal oil–water separators are also used for filtering diesel and lubricating oils by removing the waste particles and impurity from them.[3]
- 2Comparison to other types of separators
- 2.2Design and features
Mechanism[edit]
A mix of oil and water is pumped constantly into a cone-shaped separating apparatus at an angle, which creates a spinning vortex. The filtration is a result of the force balance that occurs on fluids in a vortex. High-density liquids will move to the outside, along with any contaminant, displacing the lower-density liquids to the inside (center of rotation). Water, being the more dense liquid, sits on the outside and is removed through a discharge outlet. Any segregated oil can now safely be recovered through a suction orifice at the center. The process will continue to function in this fashion as long as sufficient oil is added to maintain coverage of the suction orifice.
Comparison to other types of separators[edit]
There are other types of separators that use gravitational forces to separate mixtures, but these other types of forces are not as strong as the centrifugal force in the centrifugal separator. Other types of separators are coalescing plate pack separators and petrol interceptor separators.
Coalescing plate pack separators work very differently from centrifugal separators. With the plate packs, water is fed into the separator through gravity through the inlet pipe, then the mixture is spread evenly through the separation chamber where the coalescing plate packs are. In the plate packs the oil will rise because of their buoyancy and coalesce on the underside of the plates and form globules of oil that rise to the surface.[4] From there the waste oil globules go into the clean water chamber and are discharged through the lower portion of the separator.
With the interceptors the dirty water mixture enters the first tank of the interceptor where that tanks builds up hydrocarbons and other hazardous material in a layer. Then comes the second and third tanks of the interceptor that are all connected through pipes called 'dip pipes' which don’t allow the hydrocarbons and other contaminants to pass through. The same process that happened in the first tank will happen in the second and third tanks just with less and less contaminants.
In a centrifugal oil and water separator, the force of gravity is one-thousand[citation needed] times greater that of the coalescing plate pack separator or the petrol interceptor, so the separation is much greater. Not only is the force of separation greater, but there are fewer working parts so maintenance is much easier and cheaper.[5]
More advantages of the centrifugal oil and water separator include compact equipment size, versatility, ease of use, low cost, and high performance.[6]
Disadvantages[edit]
Centrifugal oil and water separators do have their disadvantages. One known disadvantage of these separators is that they tend to have low powered suction. For example, when the pump end is dry and the impeller is rotating at high speeds, it is simply not powerful enough to lift the oily water mixture into the separator. For this reason, these separators must always be primed before use.[7]
Design and features[edit]
Materials and metals used[edit]
The bowl of the separator is generally made up of stainless steel, brass, and bronze. The structural parts are usual[clarification needed] where the stainless steel is and the parts on the inside that come into contact with mixtures are either made of bronze or brass depending on the mixture going through the centrifugal separator. The housing and gearbox of the separator is made of aluminum or stainless steel and cast iron. The gearbox in particular is cast iron with stainless steel coating it[clarification needed].[8]
Transmission[edit]
The rotation of the separator bowl is usually powered by an electric motor, the power of which is transferred to the bowl by a transmission which may include a clutch, flexible coupling and worm gear or a centrifugal clutch connected to the vertical driving device with a flat belt.[8]
Suction and discharging of the liquids[edit]
The suction process of the separator takes place as stationary feed pipe suctions the mixture liquid into the cone-shaped pipe that feeds into the vortex. After the filtration of the liquids occur the unwanted contaminants are discharged either through an overflow or through one or two centripetal[clarification needed] pumps.[8] In case of a (combined) clarifier the solids are trapped at the outer edge of the bowl and will be discharged at intervals, except for purifiers in use for very clean liquids which may not have an opening mechanism and need to be cleaned manually.
Oily water separator
See also[edit]
References[edit]
- ^United States Patents 4,175,040, 4,959,158, 5,591,340.
- ^LaMonica, Martin (2010-06-14). 'BP Eys Kevin Costner-Backed Oil Cleanup Tech - Tech Talk - CBS News'.
- ^Smith, John (2014-11-21). 'Oil Separator Waste Recycling Equipment'.
- ^'How Oil Water Separators Work'. Anchorage Tank & Welding, Inc. Archived from the original on 2015-07-28.
- ^'Ultraspin Separators'. Ultraspin.
- ^'Lube Oil Centrifuge'. Dolphincentrifuge.com.
- ^'Advantages and Disadvantages of Centrifugal Pumps'. Construction Training and Maintenance Manuals. Archived from the original on 2015-05-15.
- ^ abc'Centrifugal separators for industrial use'(PDF). Pieralisi.com.
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