Characterisation of Bulk Solids

280 Pages·2005·3.48 MB·English

by  Don

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Characterisation of Bulk Solids
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Characterisation of Bulk Solids
Edited by
Don McGlinchey
Centre for Industrial Bulk Solids Handling
Glasgow Caledonian University, UK
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(cid:1)c 2005byBlackwellPublishingLtd
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Contents
Contributors xi
Preface xiii
1 Particlecharacterisationinbulkpowders 1
NAYLANDSTANLEY-WOOD
1.1 Introduction 1
1.1.1 Instrumentsforparticlecharacterisation 2
1.1.2 Functionalityandparticlecharacterisation 2
1.1.3 Selectionofinstrumentation 3
1.1.4 Particleaveragesandequivalentsphericaldiameter 3
1.1.5 Particle-sizedistributions 5
1.2 Metrologyofparticlecharacterisation 6
1.3 Selectedparticlecharacterisationinstruments 7
1.3.1 Directdimensionalmeasurements:Generalprinciples 7
1.3.2 Transportmeasurements:Generalprinciples 12
1.3.3 Rapidphysicalresponsemeasurements:General
principles 13
1.4 Surfaceareaandporosity:Generalprinciples 22
1.4.1 Externalandinternalsurfacearea 22
1.4.2 Porosity 23
1.4.3 On-lineandinsituparticlecharacterisation 23
1.5 Shapecharacterisationofirregularparticles 24
1.5.1 Dimensionlesssurface-volumeconversionshapefactors 25
1.5.2 Dimensionlessgeometricshapefactors 28
1.5.3 Commonindustrialusageshapefactors 31
1.5.4 Fouriertransformationorsignaturewaveforms
ofirregularparticles 31
1.5.5 Fractalgeometryofruggedirregularparticles 32
1.5.6 On-lineshapecharacterisationandmeasurement
ofparticleshape 34
1.5.7 Particleimagecontouranalysis 34
1.6 Particlehardness 36
1.6.1 Particleandmaterialhardnessbyindentation:General
principles 36
1.6.2 Macro-andmicro-indentationhardnessnumbers 37
1.6.3 Particlefracture:Griffithcrackfractureand
stress-intensityfactors 38
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1.6.4 Mohs’scaleofhardness 40
1.6.5 Abrasion,attritionandfragmentation 42
References 45
2 Bulkpropertycharacterisation 48
DONMcGLINCHEY
2.1 Howdopowdersbehave? 48
2.2 Introductiontocharacterisation 48
2.2.1 Bulkdensity 48
2.2.2 Flowability–bulkdensity 50
2.2.3 Angleofrepose 50
2.3 Introductiontotheoryandmodels 53
2.3.1 TheIdealCoulombmaterial 53
2.3.2 Moisturecontent 56
2.3.3 Wallfriction 57
2.3.4 Materialflowabilityfactor 58
2.3.5 Timeconsolidation 59
2.3.6 TheCam-claymodel 59
2.3.7 Stressdilation 61
2.3.8 Rheology 63
2.3.9 Internalstructureofagranularmaterial 64
2.3.10 Summaryofpowdermechanicsmodels 66
2.4 Sheartesters 67
2.4.1 TheJenikecell 67
2.4.2 Thetriaxialtester 68
2.4.3 Theringshearcell 70
2.4.4 Rotationalsplit-levelsheartester 71
2.4.5 Biaxialsheartesters 72
2.4.6 Uniaxialtesters 73
2.4.7 TheJohansonhang-upindiciser 73
2.4.8 Rheologicaltesters 74
2.4.9 Othertesters 75
2.4.10 Testerssummary 76
2.5 Segregation 78
2.5.1 Segregationmechanisms 79
2.5.2 Takingsamples 81
2.5.3 Characterisingsegregation 82
References 83
3 Characterisationforhopperandstockpiledesign 85
ALANW.ROBERTS
3.1 Introduction 85
3.2 Modesofflowinbins 85
3.2.1 Mass-flowandfunnel-flow 85
3.2.2 Typesofmass-flowbins 87
3.2.3 Funnel-flowbins 88
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CONTENTS vii
3.2.4 Expandedflow 89
3.2.5 Binsymmetry 89
3.3 Bulksolidparameters 90
3.3.1 Stressfieldsinmass-flowbins 90
3.3.2 Yieldlocidefiningflowofbulksolid 91
3.3.3 Instantaneousyieldloci(IYL)andflowfunction(FF) 92
3.3.4 Timeyieldloci(TYL)andflowfunction(FF) 93
t
3.3.5 Typesofflowfunctionsforbulksolids 93
3.3.6 Anglesofinternalfriction 95
3.3.7 Wallyieldlociandwallorboundaryfriction 95
3.4 Determinationofbulksolidsflowproperties 97
3.4.1 Introductoryremarks 97
3.4.2 Sheartestapparatus 98
3.4.3 Jenike-typedirectsheartester 99
3.4.4 Torsionalorringshearapparatus 101
3.4.5 Wallyieldlocus(WYL)andwallfrictionangleφ 101
3.4.6 Wallyieldloci(WYL)andwallfrictionangleφ 102
3.4.7 Bulkdensity 103
3.4.8 Permeabilityandparticlesolidsdensity 103
3.5 Mass-flowandfunnel-flowlimitsforsymmetricalbins 104
3.5.1 EstablishedtheoryduetoJenike 104
3.5.2 Modificationtomass-flowlimits–more
recentresearch 107
3.6 Determinationofmass-flowhoppergeometry 108
3.6.1 Criticalarchingdimension 108
3.6.2 Flowfactoranddesigncharts 112
3.6.3 Approximateanalyticalsolutionstothedetermination
offlowfactors 113
3.7 Mass-flowdesignexample 115
3.7.1 Limitingorcriticalgeometry 117
3.7.2 α vs.Bandflow-ratecurves 118
3.8 Funnel-flowandexpandedflowbindesign 119
3.8.1 Generalremarks 119
3.8.2 Flowpropertiesand D vs.h graph 120
f f
3.8.3 Ratholedimension, D ,vs.drawdown,h ,graph 123
f d
3.9 Ratholegeometry 124
3.9.1 Ratholeshape 124
3.9.2 Slopeofratholewalls 127
3.9.3 Archingunderfunnelflow 127
3.9.4 Drawdownandlivecapacity 128
3.10 Closingremarks 129
References 130
4 Thecharacterisationofbulkpowders 132
DEREKGELDART
4.1 Introduction 132
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4.2 Characterisationintheabsenceofanimposedgasflowthrough
thepowder 132
4.2.1 Angleofrepose 133
4.2.2 Bulkdensity 133
4.2.3 Method1:Comparativemethod 136
4.2.4 Method2:Gasflowtechnique 136
4.3 Characterisationinthepresenceofanimposedgasflowthrough
thepowder 138
4.3.1 Equipment 138
4.4 Flowandpressuredropthroughpackedbeds 138
4.5 Minimumfluidisationvelocity 139
4.6 Minimumbubblingvelocity,U 142
mb
4.7 EffectonU oftemperature,pressureandtypeofgas 143
mb
4.8 Velocityforcompletefluidisation,U 143
cf
4.9 Voidagesinfluidisedbeds 143
4.9.1 Voidageinnon-bubbling(quiescent)beds 144
4.9.2 Voidageinbubblingbeds 144
4.10 Powdergroups 146
4.10.1 GroupA 146
4.10.2 GroupB 147
4.10.3 GroupD 148
4.10.4 GroupC 148
References 149
5 Characterisationforpneumaticconveyordesign 151
MARKJONES
5.1 Introduction 151
5.2 Modesofflowinpneumaticconveying 151
5.3 Systemdesignrequirements 152
5.4 Classificationofbulkmaterialsforpneumaticconveying 153
5.4.1 TheGeldartclassificationforfluidisationbehaviour 154
5.4.2 Theuseofloose-pouredbulkdensity 155
5.4.3 Theuseofpermeabilityandde-aeration 157
5.5 Experimentaldeterminationofconveyingcharacteristics 164
5.5.1 Scalingparameters 171
5.6 Approximatemodelsfordilutephaseconveying 171
5.7 Pressure-droppredictionforfluidiseddensephaseconveying 175
5.8 Pressure-droppredictionforlow-velocityslugflow 176
References 178
Nomenclature 179
6 Characterisationofexplosibility 181
GEOFFLUNN
6.1 Introduction 181
6.2 Identificationofflammabledusts 183
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CONTENTS ix
6.3 Explosionprevention 185
6.3.1 Avoidanceofanexplosiveatmosphere 185
6.3.2 Eliminationofpotentialignitionsources 188
6.3.3 Hotsurfaceignition 191
6.4 Explosionprotection 198
6.4.1 Measuringexplosibilitycharacteristics 198
6.4.2 Explosion-protectiontechniques 201
References 204
7 Characterisationofbulkmaterials–industrialpractice 206
LYNBATES
7.1 Introduction 206
7.2 Aspectsofpowderbehaviour 214
7.2.1 Theselectionofasamplefortesting 215
7.2.2 Reasonsfortesting 217
7.3 Thebasisoftestmethods 218
7.3.1 Empiricaltests 218
7.3.2 Testsfoundeduponfundamentalprinciples 218
7.4 Mainfeatureofinterest–‘flow’ 219
7.5 Selectionofappropriatetest 220
7.5.1 ‘Quicktests’ 220
7.5.2 Measuredvaluetests 222
7.6 Bulkcharacteristicsotherthanflow 227
7.6.1 Segregation 227
7.6.2 Flushing 228
7.6.3 Caking 228
7.7 Summary 229
References 229
8 Aviewfromindustryonthecurrentindustrialbestpracticeuse
ofparticlepropertydataandwhatwillbeneededinthefuture 230
TOMTAYLOR
8.1 Particlepropertycharacterisationdata 230
8.2 Industrialbestpracticeuseofbulk-solidsparticle-sizedata 231
8.2.1 Sievedata 231
8.2.2 Electricalsensingzonetechnique 235
8.2.3 Laserdiffractionandlaserscanning 237
8.2.4 Opticalmicroscopy 239
8.2.5 Electronmicroscopy 242
8.2.6 Imageanalysis 243
8.2.7 Particle-sizeanalysis:sedimentation 245
8.2.8 Particle-sizeanalysistechniqueselection 248
8.3 Industrialbestpracticeuseofbulk-solidsparticleshapedata 249
8.3.1 Sphericity 250
8.3.2 Fractalnumber 250
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8.4 Industrialbestpracticeuseofbulk-solidsparticledensitydata 250
8.4.1 Manualmethod 251
8.4.2 Automatedmethod 251
8.5 Industrialbestpracticeuseofbulk-solidsparticle-hardnessdata 252
8.6 Futureneedsforparticlecharacterisationinbulk-solidshandling 256
8.6.1 Environment 256
8.6.2 Storage 256
8.6.3 Conveying 257
8.6.4 Energy 257
8.6.5 Long-termneeds 258
References 258
Index 259