143 114 centrifugal separators

//-->.pos {position:absolute; z-index: 0; left: 0px; top: 0px;}CENTRIFUGALS E P A R AT O R Sfor industrial useThe PrinciplesSeparationSEDIMENTATIONSedimentation is one of the mostversatile separation processes.Pieralisi Vertical Separators(Disc-Stack Separators) are ideally suited toseparation processes where thephysical characteristics ofsedimentation can be applied thanksto density difference.Centrifugal sedimentation is often avery good and economical alternativeto other separation processes such as:•Filtration:based on particle size,•Micro-Filtration:based on particlesize in the sub-micron range,The basic principle of separation bysedimentation allows for thesimultaneous separation of two orthree different, immisciblesubstances. PIERALISI VerticalSeparators that make use of thislatter separation regime are calledthree-phase separators. None of thealternative principles mentionedabove can achieve this result.Sedimentation is the physicalprocess whereby suspensions andemulsions (or a combination of both)are exposed to gravitational force,either the earth’s gravity or by usinga centrifuge. By applying g-force, thedroplets and/or particles acquiresettling velocity (vg) and are sent tothe bottom/wall of thecontainer/centrifuge bowl.Settling velocity (vg) increases with:• bigger particle diameter,• higher density difference,• lower dynamic viscosity of the fluidenvironment.Settling velocity can be estimated via awell-known equation known as Stokes’Law:SeparatorS300technicaldrawingofSeparator FPC18technical drawingseparated (stratified) within therecipient, the lightest going to thesurface, the heaviest to the bottom.(See illustration below)INCREASINGCAPACITYBut what can we do if we do not haveenough time or if we want to increasecapacity? Going back to Stokes’ Law,to obtain an higher settling velocityand consequently to accelerate thesedimentation process, we canreplace gravitational acceleration “g”by centrifugal acceleration “ˆ2r”.The centrifugal acceleration “ˆ2r”produced in a Pieralisi VerticalSeparator is up to ten thousand timeshigher than the ordinary force ofgravity “g”. As a consequence, settlingvelocity is up to ten thousand timesfaster, and separation can beachieved in a very short time and/orusing very small volumes.•Flotation:based on physical-chemical behaviour, i.e. surfacetension.In many cases centrifugalsedimentation and anothercomplementary technology arecombined to achieve the requiredprocess results.ADVANTAGESThe most common advantages ofcentrifugal sedimentation, betterknown asCentrifugal Separationare:• compact size of equipment,• low capital investment,• versatility,• ease of use,• low operating costs,• high performance.Sedimentation is used in manyindustrial processes where it isnecessary to separate substancesthat are mixed together (dispersion).With a suitable recipient and the timeneeded to complete the sedimentationprocess, the two or more substanceswith different densities will beModified Stokes’ LawN.B. Stokes’ Law can of course only be used whenthe settling process takes place under conditionswhen the Reynolds-No. is below 0,25. For higherReynolds-No., the Grassmann system has to beused, which takes advantage of two dimension-lessparameters: the Archimedes number and theOmega number.PieralisiSeparatorsPieralisi Vertical Separators combine very high rotational speed, a unique design and special materials. They generate a very highcentrifugal force which, when used for sedimentation purposes, ensures extremely efficient equipment. The mixture to beseparated is forced through a conical disc stack, where multi-layer sedimentation takes place. The separation happens very quicklyas the mixture passes through the parallel thin channels of the disc stack. A medium-sized Disc-Stack Separator, when using highcentrifugal force, can be compared to the efficiency of a sedimentation tank with a surface area of 60,000 m2, the same size as10 football fields. In technical terms, this separator hosts an “equivalent settling area” of 60,000 m2.VerticalHOW DOES IT WORK?Thousands of “g”s are produced in thebowl of the Disc Stack Separator, thecentrifugal force being the product ofthe high rotational speed and the largesize of the bowl. The rotation isgenerated by an electric motorconnected to the horizontal shaft bymeans of an elastic coupling or clutch.Thanks to the gear ratio produced byspecially-designed gears, the movementis transferred to the vertical shaft.The bowl is assembled on the conicaltop-end of the vertical shaft.The processing liquid is fed into thecentre of the bowl through thestationary feed pipe. Subsequently theinflow is accelerated by means ofspecially-designed accelerators, forcedin the first instance to the periphery ofthe bowl, and then through the discswhere multi-layer separation takesplace. The separated liquid(s) flow to thetop of the bowl where they areSECTIONOF A BOWLdischarged by overflow or by centripetalpumps. The solids captured via thedescribed settling process are collectedat the periphery of the bowl, and thendischarged intermittently. This dischargeis activated by ahydraulic systemlocated underneaththe separation area.In essence, thesolids aredischarged viaopenings at theperiphery of thebowl which areopened and closedby the down- andupwards movementof either a slidingpiston or bowlbottom (see picture).DESIGN FEATURESConstruction materialsThe structural parts of the bowl aremade of special stainless steel, theinside parts in contact with theproduct are made of suitablematerials for the processingenvironment: stainless steel, brassor bronze. The housing of theVertical Separator is in stainlesssteel or aluminium and cast iron.The gearbox is made of paintedcast iron or cast iron coated withstainless steel. The gasket materialis always selected according to theprocess media.• clutch and worm gear,• flexible coupling worm gear,• set of pulleys and flat belt.A special transmission version makesuse of a high-speed motor coupleddirectly to the vertical shaft.purposes. This version is designedfor the easy sanitization of all partsin contact with the product andrequires with no manual operation.ATEX versionSpecially-designed and certifiedVertical Separators, designed to beinstalled in hazardous areas and forthe treatment of potentiallyinflammable products, i.e.Separators complying with II2G EExcp IIB TB4. These separators areinactivated by means of nitrogen gasto minimise the risk of ignition and tofulfil ATEX requirements.Feeding and dischargeof process liquidsThe mixture generally is fed in througha stationary feed pipe in the centre ofthe bowl. The separated liquid may bedischarged from the Vertical Separatorby an overflow or by one or two built-incentripetal pumps.SPECIAL VERSIONSSanitary versionSpecially-designed all-stainless-steelSeparators, designed to be usedwith a CIP cycle for cleaningHermetic versionHydro-hermetic device installed insidethe bowl, designed to ensure thatcontact with the surroundingenvironment is avoided, and toprevent oxidation and gas leaks.TransmissionThe movement is always generatedby an electric motor and istransmitted by means of:Applicationsand TechnicalFeaturesCLARIFICATIONPURIFICATION (SEPARATION)CONCENTRATION (SKIMMING)Vertical Disc-Stack Separators are normally designed for one type of separation only, but in some cases, more versatileversions are available that can carry out two different types of separation. Below is a list of the range of disc stacks and bowldesigns used for different types of separation.Separation of suspended particles from aliquid (e.g. fruit juices, cell biomass).Separation of a heavy liquid from a main lightliquid (e.g. separation of water fromlubricating oil).Simultaneous separation of solids is also possible.Concentration of a light liquid dispersedthroughout a heavy liquid (e.g. skimming ofcream from milk).Simultaneous separation of solids is also possible.PIERALISI Disc-Stack Separatorsare able to simultaneously process dispersions of two liquids and one solid. The Pieralisi productrange offers three main equipment solutions: one with solids retention (requiring manual cleaning) known as theS-Type,oneequipped with nozzles that allow continuous solids discharge, known as theSU Type,and the other with automatic, intermittentsolids discharge, known as theFPC-Type.The tables below show types and sizes, with some general indications of dimensions.SEPARATORS WITHSOLIDS RETAINING BOWLNOZZLESSEPARATORS WITHAUTOMATIC DISCHARGETypeTotal length [mm]Total width [mm]Total height [mm]S20010007001200S25012008001400S30015008001700SU400170010001700FPC 613009001400FPC 12160012001400FPC 18170013001700FPC 24180014001900AREAS OF APPLICATION FOR PIERALISI SEPARATION SOLUTIONSEnvironmental Processestreatment and disposal processes ofsludge from municipal and industrial wastewaterdrying of animal slurrydryingof biomassthermal sludge dryingRecyclingtreatment processes for drilling mudtreatment and recovery processes forindustrial fluidsrecycling of polymersand their respective recyclablesrecyclingof service water in industrial processesoils, of bilge waterAnimal-Based Productstreatment of by-products from thefish-processing and meat-processingindustriesChemical Processesproduction processes involvingintermediate or end products andintegrated recycling and recoveryprocesses processes within HDPE,PVC and PP polymer productionproduction processes for thepharmaceutical and biotech sectorminerals and ores production processesproduction processes for non-fossil fuels,such as biodiesel and ethanolFood and Beverage Productionprocessing and recovery of non-liquid foodproducts wine and sugar processingprocessing of fruit and vegetable juicesrecycling of food-related productsOleo-chemistryproduction processes for oleo-chemistryderivatesrefining processes for ediblevegetable oils, excluding olive oilMineral- Fuel and Lube Oils Processespurification and conditioning of fuelspurification of lube oilstreatment and recovery of mineral andfuel oilstreatment of slop-oils fromrefineries and lagoons, of slops from lubeDairy Productsproduction processes of dairy andcheese products recycling of relatedwaste materialsApplicationsworldwideChemicalindustryBioethanolindustryChemical industryVegetable oils separationFuel oil purificationBiotech industrySlop oils separationRecycling industryBiodiesel glycerin separationMilk treatmentLube oil treatment

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