University of WollongongResearch Online

University of Wollongong Thesis Collection University of Wollongong Thesis Collections

1990

The application of granulation to fine coalpreparationKomaruddin AtangsaputraUniversity of Wollongong

Research Online is the open access institutional repository for theUniversity of Wollongong. For further information contact ManagerRepository Services: morgan@uow.edu.au.

Recommended CitationAtangsaputra, Komaruddin, The application of granulation to fine coal preparation, Doctor of Philosophy thesis, Department ofMechanical Engineering, University of Wollongong, 1990. http://ro.uow.edu.au/theses/1597

THE APPLICATION OF GRANULATION TO

FINE COAL PREPARATION

A thesis submitted in fulfillment of the requirements for the award of the degree

DOCTOR OF PHILOSOPHY

from

THE UNIVERSITY OF WOLLONGONG

by

KOMARUDDIN ATANGSAPUTRA, Ir.

UNIVERSITY Of WOLLONGOMC

LIBRARY

THE DEPARTMENT OF MECHANICAL ENGINEERING

19 9 0

C A N D I D A T E ' S C E R T D 7 I C A T E

This is to certify that the work presented in this thesis was conducted in the

laboratories of the Department of Mechanical Engineering, the University of

Wollongong and has not been submitted to any other university or institution for a

higher degree.

Komaruddin Atangsaputra

iii

ACKNOWLEDGEMENTS

I take this opportunity to express my deep gratitude to my supervisor , Dr.

A. G. McLean, for his excellent guidance and encouragement throughout the

conduction of this research. The completion of which was made possible by his

concern and invaluable suggestions. Particular recognition should be made for his

prominent efforts in seeking funding sources and providing experimental material.

I would also like to state my appreciation to AIDAB (Australian International

Development Assistance Bureau), the Department of Mechanical Engineering and

University of Wollongong Research Committee for funding this investigation.

Great appreciation also is extended to TAPE Wollongong Division for loan of

the conditioning and flotation cells and to Warman International Ltd. for loan of the

feed pump and hydrocyclone.

The invaluable support and assistance granted by the Workshop and Bulk

Solids Material Handling Laboratory Staff, the Department of Mechanical

Engineering, the University of Wollongong is also greatly appreciated.

I would like to state a grateful appreciation to my friend Mrs. Jeune Eshman

for her excellent assistance in English tuition.

A sincere gratitude is also extended to the Head of Mineral Technology

Development Centre, the Department of Mining and Energy, Indonesia, for his

permission to continue m y research in Australia.

Finally I would like to thank my helpful wife for her patience and loyalty.

iv

A B S T R A C T

Currently fine coal recovery and characteristic improvement are attracting

increasing attention. To exemplify this attention this thesis reports an investigation

into the application of a size enlargement process to fine coal preparation. The

application of this process was considered appropriate to overcome the existing

problems associated with the storage and flow of fine coal. In particular this

investigation aimed to identify the requirements for and characteristics of granulated

fine coal produced from coal washery waste using a drum granulator. T o this end

this investigation included the examination of techniques to produce suitable

granulator feed, the variables affecting granule strength and characteristics, the

identification of optimal binders and additive addition rates, assessment of granule

characteristics and an economic assessment of the process. O f particular concern was

the assessment of the storage and flow properties of the granulated product.

In this investigation, which utilized the pilot plant scale feed preparation and

granulation test facility at the University of Wollongong, it was found that a saleable

high quality product could be generated at high recovery rates. The production of this

product required classifying the waste coal slurry at 75 |im by use of a hydrocyclone

and processing the underflow and overflow by froth flotation and oil agglomeration

processes, respectively.

This processed material, when dried to about 18% moisture content and

mixed with suitable binders, produced granules of adequate mechanical strength and

durability. The latter mechanical strength and durability was assessed by

measurement of granule compressive strength, impact strength, standard properties

including density and particle size, flowability as assessed using a Durham Cone

tester, water immersion testing, friability or abrasion resistance and dustiness.

V

In particular it was identified that strong and stable granules could be

produced by the addition of 1.5% guar g u m or 1 % guar g u m + 0.5% bentonite. It is

subsequently shown that these granules have superior properties relative to those

exhibited by the source fine coal. In addition it is found that the granules possess

sufficient strength and durability to withstand the stresses imposed during storage,

handling and transportation.

This investigation identifies that optimum feed conditions result in optimum

granule size which in turn yields optimum granule characteristics. In particular when

using guar g u m binder optimum granules have good characteristics including

relatively low water disintegration, low friability or high abrasion resistance, low

dustiness and insensitivity to ambient humidity. These characteristics are further

improved by optimum bentonite addition rate.

These favourable characteristics in combination with the suggested favourable

process economics suggest that granulation be applied to actual coal preparation

plants. Such application will attract long term economic, environmental and

utilization benefits. The full scale application of which warrants further investigation.

vi

CONTENT

ACKNOWLEDGEMENT iii

ABSTRACT iv

CONTENTS vi

LIST OF FIGURES ix

LIST OF TABLES xvii

CHAPTER I INTRODUCTION 1

I.l General 1

1.2 Definition and Scope 5

1.3 The Objectives of the Research 6

CHAPTER II. LITERATURE REVIEW 8

CHAPTER KL THEORETICAL ANALYSIS OF GRANULATION 17

III.l Fundamental Power Attraction Forces 17

III.2 Attraction Forces Generated by Bridging Bonds 18

III.3 Liquid Binder Consumption Prediction 32

III.4 The Mechanisms of Granule Formation 48

BT.5 The Role of External Mechanical Forces on the Mechanism of Granule Formation 58

Nomenclature 65

CHAPTER IV FEED PRETREATMENT 69

IV. 1. Size Classification Using A Hydrocyclone 70

IV.2. Froth Flotation 75

IV.3. Coal Selective Agglomeration 84

Nomenclature 92

CHAPTER V FEED DEWATERING 94

V.l Some Fundamental Aspects of Dewatering 95

V.2 Residual Moisture Content of the Cake Produced by Centrifuge Dewatering 100

V.2 Dewatering Aids For Centrifuge Dewatering 105

Nomenclature 112

CHAPTER VI GRANULE POST-TREATMENT 114

VI. 1 Drying and Oil Recovery 114

VI.2 The Agglomeration/Granulation Benefits to Fine Coal Utilization 127

VI.3 Reject Material Beneficiation 138

VI.4 Environmental Considerations 140

Nomenclature 142

CHATER VII EXPERIMENTAL INVESTIGATION 144

VH.1 Apparatus Evaluation 144

VII.2 Feed Stock, Binder and Additive Evaluation 160

VII.3 Fine Coal and Granulated Product Characterization 171

VII.4 General Experimental Procedures 172

VII.5 Beneficiation Optimization and Clean Coal Production 173

VII.6 Granulation Optimization 177

VII.7 Flowability 188

VII.8 Granule Resistance to Abrasion 190

Nomenclature 190

CHAPTER VIH DISCUSSION 192

Vm.l Beneficiation Optimization and Clean Coal Production 192

VIII.2 Granulation Optimization 200

VDT.3. Untreated Fine Coal and Granule Handling Characteristics. 231

Nomenclature 240

CHAPTER IX ECONOMIC ANALYSIS 241

LX.l Capital Investment 242

LX.2 Production Cost 245

LX.3 Profitability and Decision Criteria 249

LX.4 Economic Analysis 251

Nomenclature 263

CHAPTER X CONCLUSION 264

X.l Granulation Feed Preparation 264

X.2 Granulation Optimization 265

X.3 Handleability 267

X.4 Coal Granulation Economic Assessment 268

X.5 G e n e r a l 269

X.6 Suggestions for Further Work 270

REFERENCES 275

APPENDICES 285

A. Beneficiation Optimization Test Results 285

B. The layout of me Experimental Pilot Scale Granulation Plant 288

C. Input Power Requirements for the Agglomeration Chamber 296

D. Design Considerations of the Cloth Drum Granulator 301

E. Coal and Granule Test Procedures 307

F. Granulation Test Results 312

G. Brief Procedures for Capital Investment and Operating Cost Evaluations 344

H. Plant Economic Calculation 347

I. List of Publications 359

J. Mathematical Derivations 360

ix

LIST OF FIGURES

No. Figure Page

Chapter II

II-1. Flow diagram of a pelletizing pilot plant 13

Chapter III

III-l. The states of liquid content in a granule 19

III-2. The half bridge cross section of the pendular state 20

III-3. The influence of the filling angle on the bonding force 21

III-4. Granule tensile strength vs the filling angle 22

III-5. The pendular liquid bridge between bimodal size particles 25

ffl-6. The closest packed arrangement 27

III-7. The optimum tensile strength of optimally packing particle granules 29

III- 8. The prediction of liquid consumption with the level of the pendular state 33

III-9. The half cross section of the liquid bridge in the saturated state 35

DJ-IO. The relationship between saturation and the degree of the granule state 36

HI-11. The model of optimum packing granules with closest particle configuration 38

HI-12. Binder consumption in the densest packing of polymodal granules . 40

HI-13. Mass distribution of particles forming optimally packed granules ... 42

UI-14. Size distribution of particles making up optimum packed granules .. 43

HI-15. The diameter/radius ratio between the top size and the succeeding particle size 43

rH-16. Size distribution for optimum packing particles 47

III-17. Size changes during granulation 50

111-18. Nucleation 51

IIJ-19. Granule growth region according to Sastry and Fuerstenau 52

ni-20. Development of agglomerates with increasing time 57

X

HI-21. The best dynamic loading position 59

IQ-22. Granules at the highest point of the dynamic loading position 60

PJ-23. Relation between densification factor and granulator speed for fine coal 62

IH-24. The influence of granulator diameter on densification 62

111-25. Densification factor for various materials in a drum granulator 63

HI-26. The influence of drum speed on Sf, df, and B s 65

Chapter TV

IV-1. Design and locus of zero vertical velocity in a hydrocyclone 71

TV-2. Hydrocyclone design notation 73

IV-3. The performance curve for size classification 74

IV-4. The relationship between the physical and chemical properties of fine particles and their behaviour in flotation 79

Chapter V

V-l. Saturation distribution under gravity alone 97

V-2. Saturation distribution under applied air flows 97

V-3. Pendular saturation as function of the capillary number 103

V-4. Adsorption of oil droplets on coal particles 106

V-5. Collision between coal particles and adhering oil droplets 107

V-6. Mechanism of steam dewatering 110

Chapter VI

VI-1. Cross section of segregation in coal files 130

VI-2. The effect of free moisture on coal handleability 132

VI-3. Agglomeration fine coal utilization in C O M production 136

VI-4. Settling rate of waste slurry before and after oil agglomeration 141

Chapter VII

VII-1. Combined fine coal beneficiation and granulation process pilot plant scale flowsheet 145

VII-2. Effect of specific gravity and particle size on optimum T/D ratio .... 148

xi

VII-3. Friction factor chart for a six bladed impeller 150

VII-4. A n element of the mixture 154

VH-5. Shear mixing chamber impeller details 156

VII-6. Agglomeration chamber impeller details 157

VII-7. Agglomeration chamber design 158

VII-8. Size distribution of feed samples (waste slurry) and filter cake .... 163

VII-9. Concrete mixer 178

VII-10. D r u m granulator 178

VII-11. Compressive strength tester 179

VII-12. Relationship between granule diameter and compressive strength 180

VTI-13. Consistency of the compressive strength measurement 181

VII-14. Drop test apparatus 183

VH-15. A Duplex Durham Cone 188

Chapter VIII

VIII-1. The effect of solid concentration on the cut size 193

VIII-2. Relationship between feed rate and the cut size 195

VUI-3. Influence of apex aperture on the cut size 195

VHI-4. Size distribution of filter and centrifuge cakes and waste slurry ... 198

VTII-5. Clean coal production for granulation feed 198

V m - 6 . Exp. BR-1/2 : Rosin-Rammler size distribution 199

VIII-7. Granule formation zones in the drum granulation 202

VIII-8. Granule coalescence mechanism 203

VHI-9. Granule formation zones in the concrete mixer 204

VQI-10. The effect of binder addition on the granule compressive strength 207

VIII-11. The effect of binder addition on the impact strength 208

VIII-12. The effect of binder addition on the compressive strength of granules made in the drum granulator 209

VTII-13. The effect of additives on the impact strength 210

VHI-14. The effect of additive addition on granule ash content 210

xii

VTH-15. The effect of granulation feed moisture content on granule size with 7.5% molasses binder 212

VIII-16. Frequency granule size distribution made with 7.5% molasses . 212

VB3-17. Relationship between the dso granule size and moisture content 214

VHI-18. The effect of moisture feed content on granule growth 215

VIII-19. Granule growth rate due to water addition 215

VTII-20. Relationship between granule bulk density and feed moisture content 217

VHI-21. Influence of moisture content on granule formation 218

VITI-22. Optimum water addition 219

VDI-23. Effect of granulator speed on compressive and impact strengths 220

VHI-24. Effect of extended granulator speed on compressive strength .. 221

VQI-25. Effect of granulator inclination on compressive and impact strengths 222

VTH-26. Effect of granulator inclination on granule compressive strength 222

VIII-27. Effect of granulator length on granule compressive and impact strength 223

VIH-28. Ratio between granulator length and diameter 225

VIII-29. Effect of curing on granule compressive strength 226

VDX-30. Influence of additives on granule compressive strength and curing time 227

VHI-31. The effect of soaking water time on granule compressive strength 228

VIII-32. Water disintegration index vs granule sizes 230

VDT-33. Water disintegration index vs granule sizes for the molasses granules 230

VTH-34. Water disintegration index vs granule sizes for the guar gum granules 231

VIII-35. The effect of particle size distribution on bulk density and flowability 233

VUI-36. Flowability and bulk density of untreated fine coal and granules made with 1 % guar g u m 235

Vm - 3 7 . Flowability and bulk density of untreated fine coal and granules made with 7 % molasses 235

VHI-38. Flowability of granules made with 1 % guar gum and 7 %

molasses 236

VIII-39. Friability index vs granule size 237

VIII-40. Dustiness index vs granule size 238

Vm-41. Drop number vs granule size 239

Chapter IX

LX-1. Proposed plant flowsheet for the application of granulation to fine coal preparation 244

IX-2. Effect of production rate on production cost 252

LX-3. Effect of production rate on pay out time 252

IX-4. Effect of production rate on D C F R 253

LX-5. Effect of coal feed prices on the granule production cost 255

IX-6. Effect of coal feed prices on pay out time 255

IX-7. Effect of oil and coal feed prices on production cost 257

IX-8. Effect of oil and coal feed prices on pay out time 257

IX-9. Effect of oil and coal feed prices on D C F R 257

LX-10. Effect of oil prices and consumption on production cost 258

LX-11. Effect of oil prices and consumption on pay out time 259

DX-12. Effect of oil prices and consumption on D C F R 259

LX-13. Effect of guar gum prices and production rate on production cost . 260

LX-14. Effect of guar gum prices on pay out time 260

LX-15. Effect of guar gum prices on D C F R 261

DC-16. Effect of organic material recovery and production rate on production cost 262

TX-17. Effect of organic material recovery on pay out time 262

LX-18. Effect of organic material recovery on D C F R 262

Appendix A

A-l. Size distribution of feed and products of Exp. BR-I/2 287

A-2. Partition Curve of Exp. BR-I/2 287

Appendix B

B-l. Side view of the test rig 289

B-2. Plan view of the test rig 290

Plate B-l. Pilot scale test rig general arrangement: Feed tank and pump, hydrocyclone 292

Plate B-2. Denver conditioning and flotation cells 292

Plate B-3. Dosing pump and agglomeration chamber with the background: Humbolt SO-1 Decanter Centrifuge 293

Plate B-4. Liquid binder dosing pump with the background: Humbolt SO-1 Decanter Centrifuge 293

Plate B-5. Agglomeration chamber 294

Plate B-6. Sieve bend and agglomeration chamber 294

Plate B-7. Bowl solid centrifuge : Humbolt SO-1 Decanter Centrifuge .... 295

Plate B-8. Drum granulator 295

Appendix C

C-l. Chart of agitation concentration factors 299

C-2. Chart of agitation level 300

Appendix D

D-l. The static load volume 301

D-2. The displacing and locating torque 302

D-3. Drive torque prediction 304

D-4. General arrangement and design details of the drum granulator .... 306

Appendix F

F-1. Effect of molasses addition and the granulator type on granule compressive and impact strength 316

F-2. Effect of molasses+0.5% lime and the granulator type on granule compressive and impact strength 317

F-3. Effect of molasses+1% lime and the granulator type on granule compressive and impact strength 318

F-4. Effect of molasses+0.5% bentonite and molasses+0.5% kaolin on granule compressive and impact strength 319

F- 5. Effect of auby gel and guar gum on granule compressive and impact impact strength 320

F-6. Effect of auby gel+0.5% lime and guar gum+0.5% lime on granule compressive and impact strength 321

XV

F-7. Effect of auby gel+0.5% kaolin and guar gum+0.5% kaolin on granule compressive and impact strength 322

F- 8. Effect of auby gel+0.5% bentonite and guar gum+0.5% bentonite on granule compressive and impact strength 323

F-9. Effect of molasses and lime on granule compressive strength 324

F-10. Effect of molasses and lime addition on granule impact strength ... 324

F-11. Effect of auby gel, kaolin and bentonite on granule compressive strength 325

F-12. Effect of auby gel, kaolin and bentonite on granule impact strength 326

F-13. Effect of guar gum, kaolin and bentonite on granule compressive strength 326

F-14. Effect of guar gum, kaolin and bentonite on granule impact strength 327

F-15. Effect of moisture in granulation feed on granule size distribution made with 7.5% molasses 328

F-16. The effect of feed moisture content on granule size distribution made with 3.75% molasses+0.5% lime 329

F-17. The effect of feed moisture content on granule size distribution made with 0.5 % guar gum 330

F-18. The effect of feed moisture content on granule size distribution made with 0.5 % + 0.5 % bentonite 331

F-19. The influence of feed moisture content on the granule size distribution made with 1.5 % guar gum 332

F-20. The effect of feed moisture content on frequency size distribution with binder 7.5 % molasses 333

F-21. The effect of feed moisture content on frequency size distribution with binder 0.5 % guar gum 333

F-22. The effect of feed moisture content on frequency size distribution with binder 3.75 % molasses+0.5 % lime 333

F-23. The effect of feed moisture content on frequency size distribution with binder 0.5 % guar gum+0.5 % bentonite 334

F-24. The effect of feed moisture content on frequency size distribution with binder 1.5 % guar gum 334

F-25. Effect of granule moisture content on granule compressive strength 336

F-26. Effect of lime, bentonite and kaolin on residual moisture and granule compressive strength 337

F-27. Relationship between curing time and granule moisture content with binder molasses, auby gel and guar gum 337

F-28. Relationship between curing time and granule moisture content with binder molasses and additives 338

F-29. Crushed coal and filter cake size distribution 340

xvii

THE LIST OF TABLES

No. Table Page

Chapter H

n-1. Properties of devolatilized coke pellets 12

Chapter IH

ni-1. Mass fractions of particles forming optimally packed granules 41

III-2. Mass distribution and frequency 43

III-3. Particle size vs the modulus dispersion and modulus size 45

III-4. Particle size and size distribution with n =0.6235 for the size moduli 10,100, and 1000 Lim 46

Chapter VII

VTI-1. High shear mixer configurations 154

VTI-2. Sieve and ash analysis of the feed samples using the wet method.. 162

VTI-3. Sieve analysis of the feed samples using Laser Particle Size Analyzer 162

VH-4. Filter cake size and ash distribution of flotation concentrates 164

VII-5. The composition of the domestic waste in Victoria and Australia .. 168

VII-6. Tentative granule characteristics 170

VII-7. Effect of hydrocyclone variables on the cut size 175

VH-8. Beneficiation process optimization 175

VII-9. Material balance and product quality in clean coal production 177

VII-10. Standard errors in the compressive strength measurement 181

VH-11. Optimum compressive strength of granules made in the mixer and drum granulator 184

VII-12. The effect of moisture content on granule size distribution 186

Chapter Vffl

VIII-1. Recommended operating conditions for froth flotation and oil agglomeration 196

Vni-2. Summary of Table VII-9 200

xviii

VDI-3. Yield of the optimum size granules made using different binders.. 219

VHI-4. Size distribution, bulk density and flowability of ground coal, filter cakes and centrifuge cakes produced from waste slurry rebeneficiation 232

Chapter IX

LX-1. Major equipment cost 243

LX-2. Fixed capital costs for five production rates 245

IX-3. Fixed and working capital and capital investment 245

IX-4. Power requirements 247

Appendix A

A-1. Hydrocyclone performance at operating condition of 15 % feed solid, 100 % feed valve opening and 40 % apex aperture (Exp. BR-I/2) 286

Appendix E

E-l. Product sieve analysis 311

Appendix F

F-l. Granule diameter vs compressive strength 312

F-2. The compressive strength of granules made in the concrete mixer (n=number of granules) 312

F-3. Effect of molasses addition on granule compressive and impact strength 316

F-4. Effect of molasses+0.5 % lime addition on granule compressive and impact strength 317

F-5. Effect of molasses+1 % lime addition on granule compressive and impact strength 318

F-6. Effect of molasses+0.5 % bentonite and molasses+0.5 % kaolin addition on granule compressive and impact strength in the drum granulator 319

F-7. Effect of auby gel and guar gum addition on granule compressive and impact strength 320

F-8. Effect of auby gel+0.5 % lime and guar gum+0.5 % lime addition on granule compressive and impact strength 321

F-9. Effect of auby gel+0.5 % kaolin and guar gum+0.5 % kaolin addition on granule compressive and impact strength 322

F-10. Effect of auby gel+0.5 % bentonite and guar gum+0.5 % bentonite

addition on granule compressive and impact strength 323

F-11. Size distribution of granule made using variable granulator feed moisture content with binder 7.5 % molasses 328

F-12. Size distribution of granule made using variable granulator feed moisture content with binder 3.75 % molasses+0.5 % lime 329

F-13. Size distribution of granule made using variable granulator feed moisture content with binder 0.5 % guar gum 330

F-14 Size distribution of granule made using variable granulator feed moisture content with binder 0.5 % guar gum+0.5% bentonite 331

F-15. Size distribution of granule made using variable granulator feed moisture content with binder 1.5 % guar g u m 332

F-16 Effect of the granulator operating variables on granule compressive and impact strength 335

F-17. Effect of granule curing on compressive strength and residual moisture content in granules made with molasses, auby gel and guar g u m 335

F-18. Effect of granule curing on compressive strength and residual moisture content in granules made with molasses+lime, bentonite and kaolin 336

F-19. The effect of water soaking on granule compressive strength 338

F-20. Size distribution of ground coals 339

F-21. Size distribution of ground coals and cakes 339

F-22. Effect of coal particle size on flowability (using Durham Cone, volume = 12.314 ltrs.) 340

F-23. The effect of granule size on flowability (using Durham Cone) .... 341

F-24. Effect of additive addition on granule ash content 341

F-25. Impact strength, abrasion and water resistance of granules made with 1.5 % guar g u m 342

F-26. Impact strength, abrasion and water resistance of granules made with 1 % guar gum+0.5 % bentonite 342

F-27. Impact strength, abrasion and water resistance of granules made with 7.5 % molasses 343

F-28. Impact strength, abrasion and water resistance of granules made with 7.5 % molasses+0.5 % lime 343

Appendix H

H-1. Major equipment list and costs (cost basis index 1970) for 500 tpd production 347

XX

H-2. Plant component coasts for 500 tpd production 349

H-3. Production cost estimate for the 500 tpd production plant 350

H-4. Effeet of production rate on production cost/tonne product 351

H-5. Effect of coal feedstock price on production costs 352

H-6. Effect of oil price on production costs 352

H-7. Effect of guar gum price on production costs 352

H-8. Effect of oil consumption on production costs 353

H-9. Effect of organic recovery on production costs 353

H-10. Effect of feedstock and binder/oil prices on production costs at 1,500 tpd production 353

H-ll. Profitability at various production rates 354

H-12. Effect of feedstock and oil prices on the pay out time for a 1,500 tpd production plant 355

H-13. Effect of feedstock and oil prices on D C F R for a 1,500 tpd production plant 356

H-14. Effect of plant economic variables on pay out time 356

H-15. Effect of plant economic variables on D C F R 357

H-16. Effect of oil price and consumption on production cost 357

H-17. Effect of oil price and consumption on pay out time 358

H-18. Effect of oil price and consumption on D C F R 358