Size separation of spherical particles and fibers in a centrifuge

J. AemsolSci. Vol. 29, Suppl. I, pp. S8294830, 1998 Q 1998 Published bv Elsevier Science Ltd. All rights reserved Rimed in Great Britain 0021~8502m $19.00 + 0.00

SIZE SEPARATIONOF SPHERICALPARTICLESAND FIBERSIN A CENTRIFUGE +B.ASGHARIAN and‘M. N. GOD0 ‘ChemicalIndustryInstituteof Toxicology,Research TrianglePark,NC 27709,USA ‘Fluent, Inc., Lebanon,NH USA

KEYWORDS

Centrifuge;ParticleandFiberSizeSeparation

Theaerosolcentrifugehasbeenusedto makesizedistributionmeasurements of sphericaland fibrous particles and to producenear-monodisperse aerosolpreparations.An accurate theoreticalassessment of the depositioncharacteristicsfor particlesandfibershasnot been feasible,primarily becauseof uncertaintiessurroundingtheair flow field in thecentrifuge. Experimentaldata have shown many interesting featuresof particle depositionin the centrifuge.To explainthe characteristicsof the centrifugefor particleseparation,the flow field in the centrifugeof Stoberand Flachsbart(1969)was solvedusing a commercially availablefinite elementsoftwarepackage(FIADP, Fluent,Inc., Evanston,IL USA). The flow field informationwasusedto calculatethetransportanddepositionof particlesandfibers in the centrifuge.The depositionpatternson the outer walls and depositionlength as a functionof particlediameterwerecalculated. The simulatedflow resultswerecomparedwith availableinformationin literature.The flow field wasfound to be similar to parabolicflow with the additionof strongsecondaryflows nearthe walls. The greatestsecondaryflows occurrednearthe top andbottomwalls. The transportequationsof particlesandfibersweresolvednumericallyto estimatedepositionsites on thewalls of thecentrifuge.The depositionsitesof particlesin a centrifugedepended on the particlesize,particlestartinglocationin theflow, andthe secondaryflow field. Micron-sized particlesdepositedearly andwerenot influencedby the secondaryflows. Submicron-sized particlcs(raveledthroughthecentrifuge,andtheirdepositionpatternon theouterwalls of the ccntrifugcappcarcdasacrcsccntshape,indicatingtheinfluenceof thesecondaryflows.Fiber

S830

Abstracts

of the 5th International

Aerosol

Conference

1998

depositionshowedsomedependence on fiber length.The simulatedresultsfor the particles agreedwell with thedataof Ho&miner andStober(1978). ACKNOWLEDGMENT This work wassupportedin partby grantsfrom theNorthAmericanInsulationManufacturers Associationandthe RefractoryCeramicFiberCoalition.The authorsarealsogratefulto Dr. BarbaraKuyperfor hereditorialassistance in thepreparation of this manuscript.

REFERENCES Stober,W. andFlashsbart,H. (1969)SizeSeparatingPrecipitationof Aerosolsin a Spinning SpiralDuct, Environ. Sci. Technol. 3, 1280-1296. Ho&miner, D. andStober,W. (1978)A Stober-Rotorwith Recirculationof Particle-Free Air, Am. Ind. Hyg. Assoc. J. 39, 754757.