solid liquid sep apart ion chaptre holdichfmatter

8/2/2019 Solid Liquid Sep Apart Ion Chaptre Holdichfmatter

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A. Rushton,A.S.Ward, R.G. HoldichSolid-Liquid Filtrationand Separation Technology


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0 CH Verlagsgesellschaft mbH, D-69451 Weinheim, Federal Republic of Germany, 1996

Distribution:VCH, PO. Box 101161, D-69451 Weinheim, Federal Republic of GermanySwitzerland: VCH, PO. Box, CH-4020 Basel, SwitzerlandUnited Kingdom and Ireland VCH, 8 Wellington Court, Cambridge CB1 lHZ, United KingdomUSA and Canada: VCH, 220 East 23rd Street, New York,N Y 10010-4606, USAJapan: VCH Eikow Building, 10-9 Hongo 1-chome,Bunkyo-ku,Tokyo 113, Japan

ISBN 3-527-28613-6


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A.Rushton, A. S.Ward, R.G. HoldichSolid-Liquid Filtrationand Separation Technology

VCH* einheim - New York - Base1 Cambridge - Tokyo


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Dr. Albert RushtonColynwoodClaremont DriveWest TimperleyCheshire, WA 14 SNEGreat Britain

Dr. Anthony S. WardDr. Richard G. HoldichDepartment ofChemical EngineeringLoughborough Universityof TechnologyLoughborough L El l3 TUGreat Britain

T h i s book was carefully produced. Nevertheless, authors and publisher do not warrant the informationcontained therein to be free of errors. Readers are advised to keep in mind that statements, data, illustrations,procedural details or other items may inadvertently be inaccurate.

1st edition 1996Published jointly byVCH Verlagsgesellschaft mbH, Weinheim (Federal Republic of Germany)VCH Publishers, Inc., New York, NY (USA)

Editorial Director: Dr. Barbara BockProduction Manager: Peter J. Biel

Library of Congress Card No. applied forA CIP catalogue record for this book is available from the British Library

Die Deutsche Bibliothek- CIP-EinheitsaufnahmeRushton, Albert:Solid liquid filtration and separation technology / A. Rushton ;A. S. Ward ;R. G. Holdich. -Weinheim ;New York ;Base1 ;Cambridge ;Tokyo :VCH, 1996ISBN 3-527-28613-6

0 CH Verlagsgesellschaft mbH, D-69469 Weinheim, (Federal Republic of Germany), 1996Printed on acid-free and low chlorine paperAll rights reserved (including those of translation into other languages). No part of this book may be reproducedin any form - by photoprinting, microfilm, or any other means - nor transmitted or translated into a machinelanguage without written permission from the publishers. Registered names, trademarks, etc. used in this book,even when not specifically marked as such, are not to be considered unprotected by law.Typesetting: H. Drouv6Printing and Bookbinding: Strauss Offsetdruck, D-69.509 MorlenbachPrinted in the Federal Republic of Germany


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The separation of particulate solids fiom liquids by filtration and associated techniquesconstitutes an important and often controlling stage m many industrial processes. The lattergenerate a somewhat bewildering array of particlehid separation problems. Separation byfiltration is achieved by placing a permeable filter m the path of the flowing suspension. Thebarrier, ie. a filter screen, medium or membrane m some cases is selected with a view toretaining the suspended solids on the filter surfice, whilst permitting passage of the clarifiedliquid. Other systems, e.g. deep-bed or candle filters, operate m a diBerent mode, inpromoting deposition of the particleswithinthe interstices of the medium. Further purXcationof the clarified liquid may proceed m u s e f adsorbents to remove dissolved solutes.Alternatively, the two phases may be separated by sedimentation processes, m the presence ofgravitational or cent&& force fields.Serious operational problems centre on the interaction between the particles and the filtermedium Plugging of the latter, or collapse of the collected solids under the stress caused byflow through the filter, can result m low productivity. Such effects are often related to the sizeof particles being processed; enhanced effective particle size can be accomplished by pretreatmentwith coagulants or flocculants. These techniques are discussed m detailm the text,which also reports recent improvements m the machinev of separatioq e.g. the variablechamber presses, the cross-flow processes, ceramic dewatering filters, etc.Several of these newer modifications m filtration plant have followed trends m thedeveloping science of solid-fluid separation and the growing understanding of the processesinvolved. Fortunately, filtration processes have attracted the attention of mcreasing numbersof scientists and engineers. A large output of literature has resulted m a copious flow ofdesign and operational informaton suflicient to place filtration on a much sounder scientificbasis.Nevertheless, the random nature of most particulate dispersions has resulted in a widerange of machines m thisunit operation. Selection of the best available separation techniqueis, therefore, a di&cult process problem. It is the authors viewpoint that m y xistingseparation problems would have been avoided by the application of available scientific data.This text is aimed at the provision of theoretical and practical information which can be usedto improve the possi%ddy of selecting the best equipment for a particular separation. It isrelevant to record the recent increased commercial awareness of the need for this nformatonm the selection of plant used in environmental controlThe material presented m the text has been used by the authors m short-coursepresentations over several years. These courses are illustrated by a large number of practicalproblems m the SLS field; some of these problems have been used to illustrate the book.Basic theoretical relationdqs are repeated m those chapters dealing with processcalculations. This feature minimises the need for back-referencing when using the book.A RushtonAS. WardRG. Holdich January 1996


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ContentsPreface

11.11.21.31.41.51.61.71.81.91.101.111.121.13

22.12.22.32.42.4.12.4.22.52.5.12.5.22.5.32.62.6.12.6.22.6.32.6.42.72.8

Solid Liquid Separation Technologyk RushtonIntroductionThe Filtration ProcessFiltration FundamentalsSedimentation ProcessesFilter MediaPretreatment TechniquesCMcation FjltrationSedimentation and FlotationWashing and DeliquoringMembrane FiltrationFiltration Process Equipment and CalculationsReferencesNomenclature

Filtration FundamentalsRG. HoldichIntroductionFluid Flow ThroughPorous MediaPermeabilityCake FiltrationMass Cake Deposited per Unit Area and Speczc ResistanceSolid ConcentrationForms of Cake Filtration EquationConstant Pressure FiltrationConstant Rate FiltrationVariable Pressure and Rate FiltrationEffect of Pressure on Cake FiltrationConstant Pressure FiltrationConstant Rate FiltrationAnalysis of Flow Inside a CakeVariable Rate and Pressure Filtration for Compressible CakesOther Modes of FiltrationFiltration with Non-Newtonian Fluids

1

1267

101315192426293031

33

3333363740414444485052565757636470


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VIII Contents

2.92.9.12.9.22.9.32.9.42.102.11

3

3.13.23.2.13.2.23.2.33.33.43.53.63.7

4

4.14.24.2.14.34.3.14.3.24.44.4,14.4.24.4.34.4.44.4.54.4.64.4.74.4.84.4.94.4.10

Laboratory TestsVacuum Filter LeafCompression Permeability CellCapillary Suction TimeOther Laboratory Tests and ProceduresReferencesNomenclature

Sedimentation FundamentalsA.S. WardDilute SedimentationHindered SettlingVoidage FunctionsBatch Settling: Kynch TheoryBatch FluxSettling Under Inched SurfacesNakamura-Kuroda EquationGrashof Number and SedimentationReynolds NumberReferencesNomenclature

Filter MediaA. RushtonIntroductionwoven ClothsMonofilaments and Mult3lamentsCloth SelectionEffect ofYarn Type and Weave PatternCriteria of ChoiceOperational Aspects of Woven Media in FiltersLoadingofYarnswith SolidsBacterialGrowthsPrecipitationfiom SolutionInadequate DrainageCritical ConcentrationCriticalPressureClassification ofParticlesEffect of GasBubblesEvaporation EffectsEffect of Fabric Construction

72737476778082

85

85939494989999

101105105

107

107112112114114116117117118118118120120120121122122


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Contents Ix

4.4.114.54.5.14.5.24.5.34.5 44.5 54.64.74.7.14.7.24.7.34.7.44.7.4.14.7.4.24.7.54.7.64.7.74.84.9

5

5.15.25.35.45.5

6

6.16.26.2.16.2.26.2.36.2.46.2.56.36.46.5

Effect of Cloth UnderdrainageAspects of the Cloth Selection and PerformanceCloth ShrinkageCloth stretchingFilter Cake ReleaseCloth Structural EffectsCloth Cleaning ProcessNonwoven Filter MediaMathematical Models ofFlow Through FilterMediaPermeability of Clean MediaNonwoven, Random FibreMediaWoven MediaM&if&ment Cloth PermeabilityMonofhment Cloth Permeab@Filter Pore Cloth BridgingBridge Failure and Particle BleedingHow Resistance ofUsed MediaReferencesNomenclature

Particle-stopping Power

Pretreatment TechniquesA.S. WardIntroductionCoagulation and FlocculationFilter AidsReferencesNomenclature

Clarifying FiltrationRG. HoldichCapture MechanismsDeep-Bed FiltrationPerformance.CleaningDesignLaboratory Test EquipmentDesign CalculationsPrecoat FiltrationFilter CandlesMicrostrainers

123124124125126128129130132132133135138138140143147148150152

153

153154167174175

177

178185187187188196197200202205


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X Contents

6.6 Cartridge Filtration6.6.1 Tests and Characterisation6.6.2 Filter SiZing6.6.3 Arrangements6.7 References6.8 Nomenclature

7 Sedimentationand ThickeningAS. Ward

7.1 Batch Tests and Analysis7.27.3 References7.4 Nomenclature

Design Methods for Continuous Settling

8 Centrifugal SeparationRG. Holdich; A. Rushton

8.18.1.18.1.28.28.2.18.2.28.2.38.2.48.2.58.2.5.18.2.5.28.2.5.38.2.68.2.6.18.2.78.38.3.18.3.28.3.38.3.3.18.3.3.28.3.3.38.3.48.3.58.3.6

FundamentalsAngular Velocity and AccelerationParticle Velocity in a CentrifugalField ForceCentrifugal SedimentationDesignsSimple Sigma TheoryParticle Collection EfficiencyHindered Settlingin a CentrifugeDecanter Scroll Discharge MachineApplicationsSigma Theory for Scroll Discharge DecantersPower and EfficiencyDisc Stack MachineModified Sigma TheoryDesign Calculation ExamplesHydrocyclonesCut Point and FractionationReduced Grade EfficiencyVelocitiesTangential VelocityRadialVelocityAxial VelocityLocus of Zero Vertical Velocity and MantleEquilibrium Orbit TheoryResidence Time Model

2072132182182 19220

221

221226255256

257

257257259260260261267268271272273273274275276277279281284284285286287287290


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Contenb XI

8.3.78.3.88.3.98.3.108.3.118.48.4.18.4.28.4.38.4.48.4.58.4.68.4.78.4.88.4.98.4.108.4.118.58.68.4.12

99.19.29.2.19.2.29.2.39.2.49.2.59.2 69.2.79.2.89.39.3.19.49.59.6

Dimensionless Group ModelNumerical Solutions of Continuity and FlowGeneral RelationsArrangements, Types and DesignsApplicationsCentd3gal FiltrationBatch Discharge C e n e g e sBatchDischarge Centd3ge CapacityContinuous Discharge MachinesSelection of Filtering Centd%gesCentd3ge ProductiVitiesFiltration and Permeationin CentfigationWash Timespin DryPractical Equilibrium Saturation StudiesTheoretical Filtration Rates in CentfigesCentrifkges Cake Thickness DynamicsCentrifkgal Filter DevelopmentsReferencesNomenclature

Post-Treatment ProcessesRG, HoldichIntroductionWashingWash RatioLongitudinal Dispersion, Mixing and DifhsionDiffusion CoefficientWashing EfficiencyDrained CakesStopstart WashingOther Mathematical ModelsReslurry WashingDeliquoringRelative PermeabilityEquipmentforWashing and DeliquoringReferencesNomenclature

2922952962962993003003013043053073073113 123153 17320325325326

329

3293293333373413433433433453473483513 56357357


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XI1 Contents

10

10.110.210.310.410.510.5.110.5.210.610.710.810.910.10

11

11.111.1.111.1.211.211.2.111.2.1.111.2.1.211.2.1.311.2.1.411.2.211.2.311.2.3.111.2.3.211.2.3.311.311.3.111.411.4.111.4.1.111.4.1.211.4.1.311.4.211.4.2.111.4.2.211.4.2.3

Membrane TechnologyR G . HoldichMicrofiltrationUltrafiltrationModule DesignFiltration ResistancesEquipment Scale-up and ModellingModels of Flux DeclineEquilibrium Flux ModelsDiafiltrationPermeate Flux Maintenance and RegenerationApplications and InvestigationsReferencesNomenclature

Filtration Process Equipment and CalculationsA.RushtonIn&oductionFilter Productivity FundamentalsFilter Cake Dewaterhg and WashingContinuous, Largescale FiltersRotatingDrumDrumFilter ProductivityCake Discharge and TbiclrnessTheoryvsPractice: Rotary VacuumDrum FilterDewatering and Washhg onthe RVFRotaryDisc FiltersHorizontal FiltersTihing Pan FilterRotating Table FilterHorizontal Belt FilterBatch-Operated, Large-scale Vacuum FiltersNutsche FiltersPressure FiltersFilter PressesOpthumFiltration Time CyclePractical Deviations fiomTheoretical PredictionsFatration ofHighly Compressible MaterialsVariable Chamber FiltersFilter Cake CompressionCompression KineticsVariablechamberFilter Types

359

3 633683683713 723763783883 89392393395

397

397398400406406409411413417419422422422423433433436437441446451452455455460


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Contents XI1

11.4.3 ContinuousFiltration and Expression11.4.4 Pressure Leafand Candle Filters11.5 References11.6 Nomenclature

Appendix AParticle Size, Shape and Size DistributionsParticle Size AnalysisStatistical DiametersParticle Size DistributionsCalculusof Size DistributionsSpecific SurfaceParticle Shape

AppendixBSlurry RheologyEquationsofFlowReferences

Appendix CComputer Spreadsheet Files

466470478481

483

484485486490491492

499

500502

503

Index 529

solid liquid sep apart ion chaptre holdichfmatter

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