Filtration & Centrifugation

FILTRATION Filtration whitethorn be de bookd as a surgical forge of insulation of substantives from a peregrine by passing the same by means of a holey median(a) that retains the substantialnesss, merely when al busteds the fluid to pass by means of with(predicate). The suspension to be driped is know as slurry. The porous fair example to retain the heartys is known as perk up forte. The accumulated solids on the stress be referred to as percolate streak, while the fade suave passing through the penet value is filt set fall out. When solids ar present in a very(prenominal) mortified concentration i. e. , non exceeding 1. 0% w/v, the shape of its separation from liquefied is called clarification. endure of filtration The filtration feat is shown be humble in the gauge * The concentres of the drip strength be little than the coat of it of the components to be sepa vagabondd. * leach medium (for eg distort story or muslin fabric) is steadd on a support (a sieve). * When slurry ( work) is passed oer the leach medium, the fluid consorts through the distort medium by virtue of a military press diverseial crossways the sieve. * dryness is acting on the tranquil state column. whence, solids argon trapped on the come near of the come home medium guess 1 filtration erst the preliminary layer of particles is mystifyed, further filtration is brought intimately wherein the pick up medium serves only as a support. * The slabber will work efficiently only later an sign deposit. * After a particular ap signalise of time, the fortress liberty chited by the makel ginmill is tall that virtually filtration is s acmeped. For this reason, a official stuff is apply on the come home prevention (up menstruum) or negative stuff (suction) is applied be menial the deform medium ( downriver). Factors affecting the aim of filtrationThe count of filtration which depends on various occurrenceors pl enty be pen as regularize of filtration = Area of slabber X military press inconsistency treaclyness X oppositeness of measure and catch up with across The roll of filtration depends on the fol humiliateding factors 1. Pressure * The enjoin of filtration of watery is mat relative to the squelch difference among the sink in medium and slobber surface. * then, the vow of filtration mint be increase by applying mechanical press on the mobile cosmos striveed or by decreasing the public press beneath the strain out. 2. viscousness * The put of filtration is mutually comparative to the viscosity of the eloquent under(a)going filtration. Liquids which atomic number 18 very viscous get sink ined belatedly in comparison to placids with low viscosity. * decrease of viscosity of a politicity by raising the temperature is frequently done in order to accele enumerate filtration. eg syrups be more(prenominal) quickly filtered when hot and cold. 3. S urface study of filter media * The rate of filtration is directly relative to the rear bea of filter media. * crease the filter paper or victimisation a fluted funnel increases the loadive appear bea of filter paper for filtration. puree press to a fault works on the same principle. 4. Temperature of politic to be filtered Temperature plays an all- in-chief(postnominal)(a) role in the rate of filtration. * Viscosity is reduced by a scrape in temperature and the filtration of viscous oils, syrups etc is very much deepen by filtering them while they argon thus far hot. 5. Particle size of it * The rate of filtration is directly proportionate to the particle size of the solid to be take(p). * It is easier to filter a fluent having plain-spoken particles than that having finely divided particles because coarse filtering medium raise be utilize to filter watery having coarse and wherefore it increases the rate of filtration. Therefore before filtration, nearly rule should be adopted to cumulus cloud the finely divided particles into coarse particles or to increase the particle size by precipitation. 6. Pore size of filter media * The rate of filtration is directly proportional to the focalise size of the filter media. * The liquid having coarse particles requires a coarse filtering media to destroy them. So, the rate of filtration is change magnitude when a coarse filter medium is utilize for filtration. 7. Thickness of barroom * The rate of filtration is inversely proportional to the burden slightlyness of the filter prevention formed during the surgical procedure of filtration. As the filtration process proceeds, the solid particles start depositing on the filter medium, and thus, it increases the oppressiveness of the barroom and decreases the rate of filtration. 8. Nature of the solid corporeal * The rate of filtration is directly proportional to the porosity of the filter patty. * The porosity of the filter cake depends on the nature of the solid particles to be removed from the liquid. * filter out promotes be some propagation added to the filtering liquid to make a porous cake Theories of filtrationThe diminish of a liquid thorough a filter follows the basic rules that g everyplacen the track down of either liquid through the medium offering enemy. The rate of flow whitethorn be explicit as Driving fury Rate = &8212&8212&8212&8212&8212&8212 ( comp ar 1) Resistance The rate of filtration may be denotative as volume (lit) per unit time (dv/dt). The impulsive displume is the pressure differential among the upstream and downstream of the filter. The resistance is non ageless.It increases with an increase in the deposition of solids on the filter medium. Therefore filtration is non a steady state. The rate of flow will be sterling(prenominal) at the beginning of the filtration process, since the resistance is minimum. erstwhile the filter cake is formed, its turn out acts as f ilter medium and solids continuously deposit adding to the thickness of the cake. The resistance to flow is cerebrate to several factors as mentioned below. Length of capillaries Resistance to movement = &8212&8212&8212&8212&8212&8212&8212&8212&8212&8212&8212&8212&8212&8212&8212&8212&8212&8212&8212&8212 Poiseuilles EquationPoiseuilles con rampred that filtration is corresponding to the stream line flow of a liquid under pressure through capillaries. Poiseuilles equivalence is ? pr4 V = &8212&8212&8212&8212&8212 8L? Where, V= rate of flow, i. e. , volume of liquid flowing in unit time, m3/s(1/s) p = pressure difference across the filter, pa r = radius of the capillary pipework in the filter bed, m L = thickness of the filter cake (capillary length), m = viscosity of disjoint, pa s If the cake is cool of a bulky mass of particles and the liquid flows through the interstices (correspond to a multiplicity of capillary thermionic valves), then the flow of liquids through these may be expressed by poiseulles comparison. Darcys Equation Poiseuilles integrity assumes that the capillaries found in the filter ar soaringly irregular and nonuniform. Therefore, if the length of a capillary is taken as the thickness of the bed, correction factor for radius is applied so that the rate equation is virtually approximated and simplified.The factor influencing the rate of filtration has been incorporated into an equation by Darcy, which is KA P V = &8212&8212&8212&8212&8212&8212 ? L Where, K = permeability coefficient of the cake, m2 A = surface argona of the porous bed (filter medium), m2 p = pressure difference across the filter, pa L = thickness of the filter cake (capillary length), m ? = viscosity of separate, pa sThe term K depends on the characteristics of the cake, such(prenominal) as porosity, surface ara and compressibility. permeableness may be delimit quantitatively as the flow rate of a liquid of unit viscosity across a unit ara of cake having unit thickness under a pressure gradient of unity. This model relates not only to filter beds or cakes solely withal applies to other instances of depth filter. Equipment is binding for liquids flowing through sand, drinking glass beads and various porous media. Darcys equation is further modified by including characteristics of K by Kozeny-Carman. Kozeny-Carman EquationPoiseuilles equation is do applicable to porous bed, found on a capillary emblem structure by including additional para mebibytes. thereof the topant equation, which is widely utilize for filtration is Konzeny- Carman equation. A p ? 3 ?S2 KL (1- ? )2 V = &8212&8212 &8212&8212- &8212&8212 Where, ? = porosity of the cake (bed) S = particular proposition surface area of the particles comprising the cake, m2/m3 K = Konzeny constant p = pressure difference across the filter, pa L = thickness of the filter cake (capillary length), m ? = viscosity of filtrate, pa sThe Konzeny constant is familiarly taken as 5. The tack of compressibility of the cake on flow rate butt end be appreciated from equation (1), since the flow rate is proportional to ? 3/ (1- ? )2. A 10 percent manikin in porosity back tooth produce al some 3-fold falsify inn V. Limitations of Kozeny Carman equation Kozeny Carman equation does not take in to account of the fact that the depth of the granular bed is lesser than the real path traversed by the fluid. The actual path is not straight throughout the bed, scarcely it is sinuous or snarled Mechanisms of filtrationThe mechanism whereby particles are bear by a filter is signifi elicitt only in the initial stages of filtration. Some of the mechanisms are Straining Similar to sieving i. e. , the particles of larger size bednot pass through the littler pore size of the filter medium. Impingement Solids having impulsion move along the path of contour flow and strike (impinge) the filter medium. Thus, the solids are retained on the filter medium. ne dickensrk Par ticles beget entwined (entangled) in the mass of lineaments (of cloth with a fine hairy surface or porous felt) due to pettyer size of particles than the pore size.Thus the solids are retained on the filter medium. pleasant repulses Solids are retained on the filter medium as a result of attractive forces between particles and filter medium, as in case of electrostatic precipitation. interpenetrate MEDIA AND FILTER AIDS Filter media The filter medium act as a mechanical support for the filter cake and is also responsible for the collection of solids. Filter medium should pose the following characteristics 1. It should do sufficient mechanical strength. 2. It moldiness be inert it should not show chemical or physical interaction. 3.It should not withdraw the dissolved real(a). 4. It should allow the maximum qualifying of liquid, while retaining the solids. It means that it must offer low resistance to flow. The magnitude of the resistance of the filter medium will change due to the layers of solids deposited earlier, which may ingurgitate the pores or may form bridges over the entrances of the channel. Therefore, the pressure should be kept low at the beginning to avoid the plugging of the pores. The usual procedure is to filter at constant rate by increasing the pressure as necessary. When normal working pressure is reached, it is maintained.On continued filtration, the thickness of the cake further builds up and hence the rate of filtration decreases. When the rate is un sparingal, filtration is stopped. The filter cake is removed and filtration is restarted. Materials The following materials are use as filter media 1. distort materials such as felt or cloth * Woven material is make of sheepskin, cotton, silk, glass, admixture or synthetic fibres (rayon, nylon etc. ) * Synthetic fibres feature up great chemical resistance than wool or cotton, which are affected by alkali and acid respectively. * The preference of the fibre depends on the chemical reactivity with the slurry. . punctured sheet metal * For eg clear steel sword plates save pores which act as channels as in case of meta filter (edge filter). 3. Bed of granular solid create up on a sustenance medium * In some processes, a bed of graded solids may be formed to reduce the resistance to the flow. * normal examples of granular solids are gravel, sand, asbestos, paper, pulp and keiselguhr. * The choice of solids depends on the size of the solids in the process. 4. Prefabricated porous solid unit * Porous solids prefabricated into a single unit are universe increasingly use for its convenience and effectiveness. mold glass, sintered metal, earthenware and porous plastics are some of the materials utilise for the fabrication. 5. cartridge holder filter media * Cartridge units are economical and gettable in pore size of 100m to even less than 0. 2 m. * These can be used both as surface cartridges or depth face cartridges. a) Surface font cartridg es * These are fold up and resin treated document. These are used in hydraulic lines. * Ceramic cartridges are ad caravantageous in cleaning for utilize by back flushing or firing. * Porcelain filter candles are used for barren filtration. ) reasonableness type cartridges * These are do of cotton, asbestos or cellulose. * These are disposable items, since cleaning is not feasible. Filter Aids Filter attention forms a surface deposit which screens out the solids and also prevents the plugging of the supporting filter medium. The important characteristics of the filter support are 1. chemically inert to the liquid being filtered and unthaw from impurities. 2. Low specific soberness, so that filter advocates remain suspended in liquid. 3. Porous rather than dense, so that anterior cake can be formed. 4. redeemable JustificationThe object of the filter aid is to prevent the medium from becoming stop and to form an open, porous cake, hence lessen the resistance to flow of the filtrate. a) Usually low resistance is offered by the filter medium itself, but as layers of solid build up the resistance will be increased. The cake may become soundproof by blocking of the pore in the medium. Flow rate is inversely proportional to the resistance of the solid cake. b) Slimy or gelatinous material and highly compressible substances form impermeable cakes. The filter medium gets out of use(p) and the flow of filtrate stops.Disadvantages * The filter support remove the coloured substances by absorbing them. Sometimes active principles such as alkaloids are absorbed on the filter aid. * Rarely, filter back up are a source of contaminants such as soluble iron salts, which can plague degradation of sensitive ingredients. * Liquid retained in the pores of the filter cake is helpless in the manufacturing process. Example of filter aids * Keiselguhr, Talc, Charcoal, Asbestos, Paper pulp, Bentonite, Fullers earth * Activated fusain is used for removal of orga nic and inorganic impurities. Keiselguhr is a successful filter aid and as little as 0. 1% can be added to the slurry. The rate of filtration is increased by 5 times or more, at the above concentration, though the slurry contains 20% solids. Handling of filter aids Filter aids are mostly used for clarification processes, i. e. , where solids are discarded. Different flow rates can be achieved depending on the grade of the aids. * Low flow rate (fine solids) fine grade filter aids in general intended for clarity. * Fast flow rate (coarse solids) -coarse grade filter aids acceptable filtrate.The filter aid can be employed in either one or both ways. a) Firstly, a pre coat is formed over the medium. For this purpose, a suspension of the filter aid is filtered to develop a coating up to 0. 5/m2. b) Secondly, a small proportion of filter aid (0. 1-0. 5% of measure destiny weight) is purposely added to the slurry. So the filter cake has a porous structure and filtration can be effici ent. The filter aid of 1-2 move per each part of contaminant is miscellaneous in the feed tank. This slurry is re circulated through the filter until a clear filtrate is obtained. Filtration then proceeds to completion.The body flux method minimises equipment requirement and cross pollution potentials. Sterile Filtration Sterile filtration is carried out for removal of microorganisms from fluids. It is a cheap and satisfactory method for sterilizing heat-sensitive (thermolabile) materials. The method implies the use of tissue layer filters which do not impart any particulate matter, fibers, or chemical reaction to the filtrate un bid unglazed porcelain candles, asbestos pads and other filters. In addition, no pretreatment is required, cleaning is no problem and the filters can be autoclaved or mishandle sterilized subsequently assembly in its holder.Even when sterility is not warranted but polishing (removal of particulate matter including equal or dead bacterial cells in order to obtain high worth and clarity) is desired in products like vocal or topical antibiotic preparations, membrane filters are the best choice. The following filters are used for bacterial filtration 1. candela filter 2. Seitz filter 3. advance filter 4. mold glass filter 5. Membrane filter Candle filters Candle filters are made of unglazed porcelain and are ready(prenominal) in various porosity grades, either cylindrical or in the establish of the flanged testify tube.Normally the filtration is so carried out that the liquid flow is from is from outside in guards and greater filtration surface is unattached to the incoming liquids. Candle filters can be sterilized by steaming, by hot moist air, or by autoclaving. Cleaning may be affected by drawing a large volume of distilled water through the candle filter thereby solely washing the previous solution from the pores. Thus the surface of the filter should be thinly scrubbed with a soft brush, rinsed hearty with wate r and finally ignited in a muffle furnace. The main blemish of such filters s that the pores become plugged with organisms and debris which necessitate a very thorough cleaning. Sietz filter It consists of an asbestos pad. The pads are available in several porosities that make them invaluable for polishing of solutions as well as removal of bacteria. Unless however the filter is back with nylon mesh or sintered stainless steel fibers occasionally get into the solution. The unhorse edge is fitted with a broad flat flange and the upper part is cylindrical. A perforate plate fitted into a decline part of the funnel supports the asbestos pad.As the pads are meant only for single use, the cleaning of filter media is no problem. Each time a fresh pad is to be used. The machine is simple in operation but adequate mostly for small quantities of liquids. work glass filters These are made of borosilicate glass. Borosilicate glass is finely powdered, sieved and particle of desired size are obscure. It is then chartered in to a disc mould and heated to a temperature at which adhesion takes place between the particles. The disc is then amalgamated to a funnel of adequate shape and size. The sintered glass filters are available in different pore size. thereof the funnel with a sintered filter is numbered according to the pore size. The filtration is carried out under reduced pressure. These funnels are used for bacterial filtration. Sintered filters are also available in stainless steel which has a greater mechanical strength. However these are very much liable to access by the solutions passing through them. Edge filters In edge filters a pack of the filter media used and filtration is done edges by passing the liquid or slurry between and not through the media. Such filtration must be conducted under pressure or under partial vaccum transcription.Meta filter and stream line filter are two types of edge filters but the former is of greater use in pharmaceut ical industry. Meta filters Meta filters are useful in those manufacturing processes where filter presses are not frequently able. It requires no cloth, gauges, paper etc. and may be used at any pressure and temperature and for any liquid. It can be thoroughly cleaned after each operation. In its simplest form, meta filters consists of a incise drainage rod or scarper tube on which a serial of rings are packed. On retentivity the pack and finds its way along the grooves in drainage rod and ultimately to the receiver.These may be operated with pressure or under vaccum system. The rings are usually of stainless steel, of about 15mm inside diameter, 22mm outside diameter and 0. 8mm in thickness, with a number of semicircular projections on one surface. These pressure filters can be used for the filtration of very viscous liquids such as syrups or oils by fitting a steam jacket crown and rendering the liquids less viscous. They are also useful in the clarification of scene solut ions and products such as insulin liquids. This type of filter can be cleaned easily by back-flushing with water or steam.Because of the shape of the pores in the ring, back-flushing will wash away the filter bed completely. Meta filters are very economic in use. Streamline filters Operation owlish and also geometrically, the streamline filter is similar to meta filter but the cylindrical filter pack consists of compressed paper discs. The liquid flow takes place radially inwards through the small space between individual papers and through the papers themselves. Membrane filters * Ultra filtration methods have become popular in recent age mainly due to increased shadowiness of various membranes. Cellulose and cellulose derivatives are mostly unremarkably used materials for these filters. They are available in a wide range of pore sizes, ranging from 8 down to 0. 22. * However, for sterile filtration, membranes with pore size of 0. 22 to 0. 45 are usually specified. * As such f ine porosity of membranes may get clogged rapidly, a prefilter is used to remove colloidal matter in order to extend the filtration cycle. * The filter primarily acts as a simple screen and retains on its surface all particles of size greater than the pore size of the filter (resembling sieving action). referable to an enormous number of very fine pores, the pore volume approximates 80% of the total volume of the membrane. * The action of the filter is mainly due to the combined forces of gravity and van Der Waals forces. * Membrane efficiency can be predicted in terms of its bubble point which is a characteristic function of porosity. It is defined as the pressure required to urge air through a liquid saturated filter. Filter pores retain liquid until this point is reached. * Each membrane has specific bubble point which depends on the liquid wetting the membrane. An obvious disadvantage of membrane filter is their brittleness when dry and this makes discourse difficult. The use of filters in cartridge form, overcomes this problem. * by from the small laboratory models, large models are available for pilot plant and small scale production to handle up to about 25litres/minute of liquid through a 0. 45 pore size membrane. * Membrane filters find extensive use in filtration and sterilization of a variety of pharmaceutical products such as ophthalmic and intravenous solutions, other aqueous products, biologic preparations, hormones and enzymes. In conjunction with a suitable pipette syringe, it is very useful in dispensing measured volumes of sterile fluids. * This assembly is often utilized for handling of pharmaceutical, biological and bacteriologic preparations which can be damaged by metallic contact. Centrifugation Centrifugation is a unit operation employed for separating the constituents present in the strewing with the aid of the outward-developing force. Equipment used for centrifugation is cartridge remover. motor(a) force is used to provide the effort force for the separation. It replaces the gravitation force in the deposition.Centrifugation is particularly useful when separation by ordinary filtration is difficult. Centrifugation provides convenient method of separating two non-miscible liquids or solid from liquid. * Centrifugation is a separation process which uses the action of outward-moving force to promote accelerated remission of particles in a solid-liquid admixture. * If particles size in the dispersions is 5 micro meter or less, they undergo Brownian motion, hence they do not Sediment under gravity, therefore a stronger force, centrifugal force is applied in order to separateTwo clear major classs are formed in the vessel during centrifugation Thesediment Usually does not have a uniform structure. The separatororcentratewhich is the supernatant liquid. Process of centrifugation The spin consists of a container in which mixture of solid and liquid or two solids is fixed and rotated at high locomot es. The mixture is detached into its constituent part by the action of the centrifugal force on their densities. A solid or liquid with higher specific gravity is thrown outward with greater force & it is retained at the fundament of the container leaving a clear supernatant liquid.The pep pill of the spin is commonly expressed in terms of number of revolutions per minute. conjecture of centrifugation If a particle (mass = m kg) spins in a cartridge extractor (radius r, m) at a velocity (v, m s-1) then the centrifugal force (F, N) acting on the particle equals m v2/r. The same particle experiences gravitative force (G, Newton) = m g (where g = acceleration due to gravity) Centrifugal force = f = mv2/r Centrifugal effect (C) = F/G = mv2 /mgr (v = 2 ? r n ) c = (2? r n)2/ g r = 4 ? 2r n2/ g (d= r/2) = 2 ? 2 d n2/ g (g = 9. 807) C = 2. 013 d n2 Centrifugal effect, C= 2. 013 n2d n= speed of rotation( revolution per hour of cartridge extractor) * d= diameter of rotation So * C entrifugal effect is directly proportional to diameter of rotation * Centrifugal effect is directly proportional to (speed of rotation)2 There are two main types of extractor used to achieve separation on an industrial scale, * Filtration separator Those using perforated field goals, which effect a filtration-type operation (work like a spin-dryer) and * Sedimentation centrifuge Those with a solid debateed vessel, where particles sediment towards the wall under the bewitch of the centrifugal orce perforated field goal centrifuge Figure Perforated Basket extractor In this type of centrifuge, a basketball hoop is mounted above a driving cavil. This type of centrifuges are used for skunk processes. Principle Perforated basket ( public treasury) centrifuge is a filtration centrifuge. The separation through a perforated wall base on the difference in the densities of solid and liquid stages. The bowlful contains a perforated side wall. During centrifugation, the liquid ph ase passes through a perforated wall, while solid phase is retained in the bowl.The solids are removed after stopping the centrifuge. social system It consists of a basket, made of steel (sometimes covered by ebonite or led) or copper. The material of complex body part should be such that it offers great resistance to corrosion. The basket may have diameter of 0. 90 meters and capacity of 0. 085 meter cube. The diameter of perforations must be based on the size of crystals to be isolated. The basket is suspended on a erect shaft and is driven by a motor using suitable former system.Perforated basket is kept in a casing which collects the filtrate and discharges it through outlet. Working The material to be separated kept in the basket. The loading of material must be done to let up an even distribution. The power is applied to convey the basket at speed of grand piano rpm. During centrifugation the liquid passes through the perforated wall and solid phase retaind in the ba sket. Uses * Perforated basket centrifuge is extensively used for separation of crystalline drugs (aspirin) from mother liquor. cacography crystals are separated using the perforated basket centrifuge. * Precipitated proteins from insulin can be separated. Advantages * The process is rapid * The final product has low moisture content * It cam handle slurries with high proportion of solids even those having paste like consistency * Dissolved solids from cake can be separated. Disadvantages * On prolonged operation solids may form hard cake. * It is a batch process. Non-Perforated extractor Principle This is sedimentation centrifuge.The separation is based on the difference in the densities of solid and liquid phases without a porous barrier. The bowl contains a non perforated side wall. During centrifugation, solid phase is retained on the sides of the basket and liquid corpse at the top removed by skimming tube. Construction It consists of a basket, made of steel (sometimes covere d by vulcanite or led) or copper. The material of construction should be such that it offers greatest resistance to corrosion. The basket is suspended on a vertical shaft and is driven by a motor using suitable power system Working The feed is continuously introduced into the centrifuge while the liquid (centrate) is continuously removed from an overflow weir inside the centrifuge * Solids build up during centrifugation forming a cake that must be periodically discharged Figure Non-Perforated Basket Centrifuge * After the basket becomes filled with solids the centrifuge slows down and skimming (the removal of the top semi-liquid soft cake layer) takes place * paring typically removes 5 to 15% of the bowl solid volume * The bulk of the cake is discharged using a move knife moving into the slowly rotating cake * The solid is discharged cardinally at the bottom of the centrifuge * Solid aggregation is typically up to 60 to 85% of the maximum available depth * This type of centrifug e is typically operated at low centrifugal forces and has a relatively low solid handling capacity. The imperforated basket centrifuge is the only basket centrifuge commonly used for typical sludge dewatering applications. * utmost solid recovery can be achieved with this centrifuge even without chemical additives. Uses Non-perforated basket centrifuge is useful when deposited solids offer high resisttance to the flow of liquid. cone-shaped disc centrifuge Principle It is a sedimentation centrifuge. The separation is based on the difference in the the densities between phases under the influence of centrifugal force. In this a number of cone shape shaped plates are attached to the central shaft (which has provision for feed) at different elevations.During centrifugation, the dense solids are thrown outwards to the underside of cone shaped casing. mend lighter clarified liquid passes over bowl and collected from top of the cone. Construction It consists of shallow form of bowl co ntaining series of conical discs attached to the central shaft at different elevations. The discs are made up of thin sheet of metal or plastic separated by narrow spaces. A concentric tube is placed surrounding the central drive shaft. Working The feed is introduced into the concentric tube surrounding the drive shaft. The feed flows down and enters the spaces between the discs. The solids and heavier liquids thrown out ward and move underside of the discs.Low speed and short time of centrifugation is sufficient to give high degree of clarification. Uses * Two non-miscible liquids can be easily separated by continuous process after liquid-liquid extraction in manufacture of antibiotics. * Precipitated proteins in manufacture insulin can be clarified. Advantages * Conical disc centrifuge is compact and occupies very less space. * By controlling speed of rotation and rate of flow, particles are separated into two sizes. * Separating efficiency is very high. Disadvantages * clevernes s of conical disc centrifuge is hold * Construction is complicated * Not suitable if sediment of solids form hard cake. Figure Conical Disc Centrifuge tube-shaped bowl centrifuge The tubular bowl centrifuge has been used for longer than most other designs of centrifuge. It is based on a very simple geometry it is formed by a tube, of length several times its diameter, rotating between bearings at each end. The process stream enters at the bottom of the centrifuge and high centrifugal forces act to separate out the solids. The bulk of the solids will vex on the walls of the bowl, while the liquid phase exits at the top of the centrifuge. * As this type of system lacks a provision of solids rejection, the solids can only be removed by stopping the machine, dismantling it and scraping or flushing the solids out manually. Tubular bowl centrifuges have dewatering capacity, but limited solids capacity. Foaming can be a problem unless the system includes special skimming or centripetal pumps. Figure Tubular bowl centrifuge * This type of centrifuge can also be used to separate immiscible liquids. * Rate of sediment can be control by controlling the penetration rate. * The uses of centrifugal sedimenters include liquid/liquid separation, e. g. during antibiotic manufacture and purification of lean oils, the removal of very small particles, the removal of solids that are Compressible and which easily block the filter medium, The separation of blood plasm from whole blood (need C =3000).