Volume 2

7 Pulp Bleaching 609

Herbert Sixta, Hans-Ullrich Suss, Antje Potthast, Manfred Schwanninger,

and Andreas W. Krotscheck

7.1 General Principles 609

7.2 Classification of Bleaching Chemicals 610

7.2 Bleaching Operations and Equipment 613

Andreas W. Krotscheck

7.2.1 Basic Rheology of Pulp-Liquor Systems 614

7.2.2 Generic Bleaching Stage Set-Up 616

7.2.3 Medium Consistency Pumps 617

7.2.4 Medium Consistency Mixers 619

7.2.4.1 High-Shear Mixers 620

7.2.4.2 Static Mixers 621

7.2.4.3 Atmospheric Steam Mixers 622

7.2.5 Medium Consistency Reactors 623

7.2.5.1 Atmospheric Upflow Reactors 623

XII Contents

7.2.5.2 Atmospheric Downflow Reactors 624

7.2.5.3 Pressurized Reactors 625

7.2.6 Blowtank 627

7.2.7 Agitators 627

7.2.8 Washing 628

7.3 Oxygen Delignification 628

7.3.1 Introduction 628

7.3.2 Chemistry of Oxygen Delignification 632

Manfred Schwanninger

7.3.2.1 Bleachability 634

7.3.2.2 Lignin Structures and their Reactivity 634

7.3.2.3 Oxygen (Dioxygen) and its Derivatives 641

7.3.2.4 A Principal Reaction Schema for Oxygen Delignification 649

7.3.2.5 Carbohydrate Reactions in Dioxygen-Alkali Delignification

Processes 657

7.3.2.6 Residual Lignin–Carbohydrate Complexes (RLCC) 666

7.3.2.7 Inorganics (Metals) and their Role in the Protection/

Degradation of Cellulose 668

7.3.3 Mass Transfer and Kinetics 671

Herbert Sixta

7.3.3.1 Kinetics of Delignification 672

7.3.3.2 Kinetics of Cellulose Chain Scissions 685

7.3.3.3 Application of Surfactants 687

7.3.4 A Model to Predict Industrial Oxygen Delignification 688

7.3.4.1 Theoretical Base of the van Heiningen Model 690

7.3.4.2 Case Study 695

7.3.5 Process Variables 701

7.3.5.1 Temperature 701

7.3.5.2 Retention Time 702

7.3.5.3 Alkali Charge 703

7.3.5.4 pH Value 704

7.3.5.5 Final pH 705

7.3.5.6 Alkali Source 706

7.3.5.7 Oxygen Charge, Oxygen Pressure 707

7.3.5.8 Consistency 708

7.3.6 Pulp Components and Impurities 708

7.3.6.1 Effect of Metal Ion Concentration 708

7.3.6.2 Residual Lignin Structures 713

7.3.6.3 Carry-Over 716

7.3.6.4 Xylan Content 719

7.3.6.5 Selectivity of Oxygen Delignification 720

7.3.7 Process and Equipment 721

7.3.7.1 MC versus HC Technology 721

7.3.7.2 Process Technology 722

7.3.7.3 Process Equipment 731

Contents XIII

7.3.8 Pulp Quality 733

7.4 Chlorine Dioxide Bleaching 734

7.4.1 Introduction 734

7.4.2 Physical and Chemical Properties and Definitions 735

7.4.2.1 Behavior of Chlorine Dioxide in Aqueous Solution 737

7.4.2.2 Inorganic Side Reactions during Chlorine Dioxide Bleaching of Wood

Pulps 737

7.4.3 Generation of Chlorine Dioxide 741

7.4.4 Chemistry of Chlorine Dioxide Treatment 745

Manfred Schwanninger

7.4.4.1 Chlorination Products 752

7.4.5 Performance of Chlorine Dioxide Bleaching 754

7.4.5.1 Standard Chlorine Dioxide Bleaching 754

7.4.5.2 Chlorine Dioxide Bleaching of Oxygen-Delignified Kraft Pulps 759

7.4.5.3 Modified Chlorine Dioxide Bleaching 761

7.4.6 Technology of Chlorine Dioxide Bleaching 770

Andreas W. Krotscheck

7.4.7 Formation of Organochlorine Compounds 771

7.5 Ozone Delignification 777

7.5.1 Introduction 777

7.5.2 Physical Properties of Ozone 778

7.5.3 Ozone Generation 782

7.5.4 Chemistry of Ozone Treatment 785

Manfred Schwanninger

7.5.4.1 Ozone Decomposition 786

7.5.4.2 Degradation of Lignin 790

7.5.4.3 Degradation of Carbohydrates 794

7.5.5 Process Conditions 798

7.5.5.1 Mass Transfer 798

7.5.5.2 Mixing and Mixing Time 802

7.5.5.3 Effect of Pulp Consistency 806

7.5.5.4 Effect of pH 811

7.5.5.5 Effect of Temperature 813

7.5.5.6 Effect of Transition Metal Ions 814

7.5.5.7 Effect of Carry-Over 816

7.5.5.8 Effect of Pretreatments and Additives 818

7.5.5.9 Effect of Sodium Borohydride after Treatment 822

7.5.5.10 Effect of Alkaline Extraction 824

7.5.6 Technology of Ozone Treatment 826

Andreas W. Krotscheck

7.5.6.1 Medium-Consistency Ozone Treatment 826

7.5.6.2 High-Consistency Ozone Treatment 827

7.5.6.3 Ozone/Oxygen Gas Management 828

7.5.7 Application in Chemical Pulp Bleaching 829

7.5.7.1 Selectivity, Efficiency of Ozone Treatment of Different Pulp Types 829

XIV Contents

7.5.7.2 Effect of Ozonation on the Formation of Carbonyl and Carboxyl

Groups 840

7.5.7.3 Effect of Ozonation on Strength Properties 841

7.5.7.4 Typical Conditions, Placement of Z in a Bleaching Stage 843

7.6 Hydrogen Peroxide Bleaching 849

Hans-Ullrich Suss

7.6.1 Introduction 849

7.6.2 H2O2 Manufacture 850

7.6.3 Physical Properties 850

7.6.4 Chemistry of hydrogen peroxide bleaching 853

Manfred Schwanninger

7.6.4.1 Decomposition of H2O2 854

7.6.4.2 Residual Lignin 856

7.6.4.3 Carbohydrates 859

7.6.5 Process Parameters 860

Hans-Ullrich Suss

7.6.5.1 Metals Management 860

7.6.5.2 Alkaline Decomposition of H2O2 862

7.6.5.3 Thermal Stability of H2O2 and Bleaching Yield 863

7.6.5.4 Pressurized Peroxide Bleaching 866

7.6.6 Technology of H2O2 Bleaching 866

Andreas W. Krotscheck

7.6.6.1 Atmospheric Peroxide Bleaching 866

7.6.6.2 Pressurized Peroxide Bleaching 867

7.6.7 Application in Chemical Pulp Bleaching 868

Hans-Ullrich Suss

7.6.7.1 Stabilization of Brightness with H2O2 873

7.6.7.2 Catalyzed Peroxide Bleaching 877

7.6.7.3 Application in TCF Sulfite Pulp Bleaching 877

7.6.7.4 Activators for H2O2 Bleaching 880

7.7 Peracetic Acid in Pulp Bleaching 880

7.8 Hot Acid Hydrolysis 883

7.9 Alternative Bleaching Methods 885

7.10 Bleach Plant Liquor Circulation 887

Andreas W. Krotscheck

7.10.1 Introduction 887

7.10.2 Intra-Stage Circulation and Circulation between Stages 888

7.10.3 Open and Closed Operation of Bleaching Stages 890

7.10.4 Construction Material Compatibility 893

7.10.5 Implications of Liquor Circulation 893

Contents XV

8 Pulp Purification 933

Herbert Sixta

8.1 Introduction 933

8.2 Reactions between Pulp Constituents and Aqueous Sodium Hydroxide

Solution 935

8.3 Cold Caustic Extraction 942

8.3.1 NaOH Concentration 942

8.3.2 Time and Temperature 944

8.3.3 Presence of Hemicelluloses in the Lye 945

8.3.4 Placement of CCE in the Bleaching Sequence 948

8.3.5 Specific Yield Loss, Influence on Kappa Number 949

8.3.6 Molecular Weight Distribution 951

8.4 Hot Caustic Extraction 952

8.4.1 Influence of Reaction Conditions on Pulp Quality and Pulp Yield 953

8.4.1.1 NaOH Charge and Temperature in E, (EO), and (E/O) Treatments 953

8.4.1.2 Xylan versus R18 Contents 957

8.4.1.3 Purification versus Viscosity 959

8.4.1.4 Purification versus Kappa Number and Extractives 960

8.4.1.5 Composition of Hot Caustic Extract 961

8.4.2 MgO as an Alternative Alkali Source 962

9 Recovery 967

Andreas W. Krotscheck and Herbert Sixta

9.1 Characterization of Black Liquors 967

9.1.1 Chemical Composition 967

9.1.2 Physical Properties 970

9.1.2.1 Viscosity 970

9.1.2.2 Boiling Point Rise (BPR) 970

9.1.2.3 Surface Tension 971

9.1.2.4 Density 971

9.1.2.5 Thermal Conductivity 972

9.1.2.5 Heat Capacity [8,11] 972

9.2 Chemical Recovery Processes 973

9.2.1 Overview 973

9.2.2 Black Liquor Evaporation 974

9.2.2.1 Introduction 974

9.2.2.2 Evaporators 975

9.2.2.3 Multiple-Effect Evaporation 977

9.2.2.4 Vapor Recompression 979

9.2.3 Kraft Chemical Recovery 980

9.2.3.1 Kraft Recovery Boiler 980

9.2.3.2 Causticizing and Lime Reburning 986

9.2.3.3 The Future of Kraft Chemical Recovery 992

9.2.4 Sulfite Chemical Recovery 994

XVI Contents

10 Environmental Aspects of Pulp Production 997

Hans-Ulrich Suss

10.1 Introduction 997

10.2 A Glimpse of the Historical Development 998

10.3 Emissions to the Atmosphere 1002

10.4 Emissions to the Aquatic Environment 1004

10.5 Solid Waste 1006

10.6 Outlook 1007

11 Pulp Properties and Applications 1009

Herbert Sixta

11.1 Introduction 1009

11.2 Paper-Grade Pulp 1010

11.3 Dissolving Grade Pulp 1022

11.3.1 Introduction 1022

11.3.2 Dissolving Pulp Characterization 1024

11.3.2.1 Pulp Origin, Pulp Consumers 1024

11.3.2.2 Chemical Properties 1026

11.3.2.3 Supramolecular Structure 1041

11.3.2.4 Cell Wall Structure 1047

11.3.2.5 Fiber Morphology 1051

11.3.2.6 Pore Structure, Accessibility 1052

11.3.2.7 Degradation of Dissolving Pulps 1056

11.3.2.8 Overview of Pulp Specification 1060

II Mechanical Pulping 1069

Jurgen Blechschmidt, Sabine Heinemann, and Hans-Ulrich Suss

1 Introduction 1071

Jurgen Blechschmidt and Sabine Heinemann

2 A Short History of Mechanical Pulping 1073

Jurgen Blechschmidt and Sabine Heinemann

3 Raw Materials for Mechanical Pulp 1075

Jurgen Blechschmidt and Sabine Heinemann

3.1 Wood Quality 1075

3.2 Processing of Wood 1076

Contents XVII

3.2.1 Wood Log Storage 1076

3.2.2 Wood Log Debarking 1076

3.2.3 Wood Log Chipping 1078

4 Mechanical Pulping Processes 1079

Jurgen Blechschmidt and Sabine Heinemann

4.1 Grinding Processes 1079

4.1.1 Principle and Terminology 1079

4.1.2 Mechanical and Thermal Processes in Grinding 1080

4.1.2.1 Softening of the Fibers 1080

4.1.2.2 Defibration (Deliberation) of Single Fibers from the Fiber

Compound 1083

4.1.3 Influence of Parameters on the Properties of Groundwood 1084

4.1.4 Grinders and Auxiliary Equipment for Mechanical Pulping by

Grinding 1087

4.1.4.1 Pocket Grinders 1089

4.1.4.2 Chain Grinders 1090

4.1.4.3 Pulp Stones 1092

4.1.5 Pressure Grinding 1095

4.2 Refiner Processes 1098

4.2.1 Principle and Terminology 1098

4.2.2 Mechanical, Thermal, and Chemical Processes in the Refiner

Process 1100

4.2.3 Machines and Aggregates for Mechanical Pulping by Refining 1104

5 Processing of Mechanical Pulp and Reject Handling: Screening and

Cleaning 1113

Jurgen Blechschmidt and Sabine Heinemann

5.1 Basic Principles and Parameters 1113

5.2 Machines and Aggregates for Screening and Cleaning 1114

5.3 Reject Treatment and Heat Recovery 1121

6 Bleaching of Mechanical Pulp 1123

Hans-Ulrich Suss

6.1 Bleaching with Dithionite 1124

6.2 Bleaching with Hydrogen Peroxide 1126

6.3 Technology of Mechanical Pulp Bleaching 1134

7 Latency and Properties of Mechanical Pulp 1137

Jurgen Blechschmidt and Sabine Heinemann

7.1 Latency of Mechanical Pulp 1137

7.2 Properties of Mechanical Pulp 1138

XVIII Contents

III Recovered Paper and Recycled Fibers 1147

Hans-Joachim Putz

1 Introduction 1149

2 Relevance of Recycled Fibers as Paper Raw Material 1153

3 Recovered Paper Grades 1157

3.1 Europe 1157

3.2 North America and Japan 1161

3.2.1 United States 1162

3.2.2 Japan 1163

4 Basic Statistics 1165

4.1 Utilization Rate 1167

4.2 Recovery Rate 1170

4.3 Recycling Rate 1173

4.4 Deinked Pulp Capacities 1174

4.5 Future Development of the Use of Recovered Paper 1175

5 Collection of Recovered Paper 1177

5.1 Pre-Consumer Recovered Paper 1178

5.2 Post-Consumer Recovered Paper 1178

5.2.1 Pick-Up Systems 1178

5.2.2 Drop-Off Systems 1179

5.3 Efficiency of Different Collection Systems 1180

5.4 Municipal Solid Waste 1181

6 Sources of Recovered Paper 1183

7 Sorting, Handling, and Storage of Recovered Paper 1187

7.1 Sorting 1187

7.2 Handling 1189

7.3 Storage 1190

8 Legislation for the Use of Recycled Fibers 1191

8.1 Europe 1192

8.2 United States of America 1195

8.3 Japan 1198

Appendix: European List of Standard Grades of Recovered Paper and

Board (February, 1999) 1203

Contents XIX

IV Analytical Characterization of Pulps 1211

Erich Gruber

1 Fundamentals of Quality Control Procedures 1213

1.1 The Role of QC 1214

1.2 Basics of QC-statistics 1214

1.3 Sampling 1216

1.4 Conditions for Testing and/or Conditioning 1216

1.5 Disintegration 1217

2 Determination of Low Molecular-Weight Components 1219

2.1 Moisture 1219

2.2 Inorganic Components 1219

2.2.1 Ashes 1220

2.2.1.1 Total Ash 1220

2.2.1.2 Sulfated Ash 1220

2.2.1.3 Acid-Insoluble Ash 1220

2.2.2 Determination of Single Elements 1221

2.2.2.1 Survey of Chemical Procedures 1221

2.2.2.2 Atomic Absorption Spectroscopy (AAS) 1222

2.2.2.3 X-ray Fluorescence Spectroscopy (XFS) 1223

2.2.2.4 Electron Spectroscopy for Chemical Application (ESCA) 1223

2.3 Extractives 1224

2.3.1 Water Extractives 1224

2.3.1.1 Test Water 1224

2.3.1.2 Cold Water Extraction 1225

2.3.1.3 Hot Water Extraction 1225

2.3.1.4 Analysis of Water Extracts 1225

2.4 Chlorine Compounds 1225

3 Macromolecular Composition 1227

3.1 Lignin Content 1227

3.2 Extent of Delignification 1228

3.2.1 Roe Number 1228

3.2.2 Chlorine Number 1228

3.2.3 Kappa Number (Permanganate Number) 1228

3.3 Alkali Resistance and Solubility 1229

3.3.1 Alkali-Soluble Components 1229

3.3.2 a -, b -, and c -cellulose 1229

3.3.3 R18 and S18 values 1230

3.4 Composition of Polysaccharides 1231

3.4.1 Determination of Monosaccharides after Hydrolysis 1231

3.4.1.1 Gas Chromatography 1231

3.4.1.2 Thin-Layer Chromatography 1232

XX Contents

3.4.1.3 Liquid Chromatography 1232

3.4.2 Determination of Pentosans after Hydrolysis 1233

3.4.3 Determination of Uronic Acids after Hydrolysis 1233

3.5 Functional Groups 1234

3.5.1 Carbonyl Functions 1234

3.5.1.1 Copper Number 1235

3.5.1.2 Sodium Borohydride Method 1236

3.5.1.3 Hydrazine Method 1236

3.5.1.4 Oxime Method 1236

3.5.1.5 Girard-P Method 1237

3.5.1.6 Cyanohydrin Method 1237

3.5.1.7 Fluorescent Dying 1237

3.5.2 Carboxyl Functions 1238

3.6 Degree of Polymerization (Molecular Mass) 1239

3.6.1 Solvents for Cellulose 1240

3.6.1.1 CUOXAM 1241

3.6.1.2 CUEN 1241

3.6.1.3 Iron Sodium Tartrate (EWNN) 1241

3.6.2 Diverse Average Values of Molecular Mass and Index of

Nonuniformity 1241

3.6.3 Methods to Determine Molar Mass (“Molecular Weight”) 1243

3.6.3.1 Osmosis 1243

3.6.3.2 Scattering Methods 1245

3.6.4 ViscosityMeasurements 1248

3.6.4.1 Solution Viscosity as a Measure of Macromolecular Chain Length 1248

3.6.4.2 ViscosityMeasurements on Cellulose Pulps 1251

3.6.5 Molecular Weight Distribution 1251

3.6.5.1 Fractional Precipitation or Solution 1251

3.6.5.2 Size-Exclusion (Gel-Permeation) Chromatography 1252

4 Characterization of Supermolecular Structures 1257

4.1 Crystallinity 1257

4.1.1 Degree of Crystallinity 1257

4.1.1.1 X-Ray Diffraction 1259

4.1.1.2 Solid-phase NMR-Spectroscopy 1261

4.1.1.3 Reaction Kinetics 1262

4.1.1.4 Density Measurements 1262

4.1.2 Dimension of Crystallites 1263

4.1.3 Orientation of Crystallites 1265

4.2 Accessibility, Voids, and Pores 1265

4.2.1 Porosity 1266

4.2.2 Accessible Surface 1267

4.3 Water and Solvent Retention 1268

Contents XXI

4.3.1 Total Water Uptake 1268

4.3.2 Free and Bound Water 1268

5 Fiber Properties 1269

5.1 Identification of Fibers 1269

5.1.1 Morphological Characterization 1269

5.1.2 Visible and UV Microscopy 1271

5.1.3 Electron Microscopy 1271

5.2 Fiber Dimensions 1272

5.2.1 Fiber Length and Width 1273

5.2.1.1 MicroscopicMethods and Image Analysis 1273

5.2.1.2 Fiber Fractionation by Screening 1274

5.2.2 Coarseness 1275

5.3 Mechanical Properties 1275

5.3.1 Single Fiber Properties 1275

5.3.1.1 Wet Fiber Properties 1275

5.3.1.2 Mechanical Properties of Dry Fibers 1277

5.3.2 Sheet Properties 1278

5.3.2.1 Preparation of Laboratory Sheets for Physical Testing 1278

5.3.2.2 Determination of Mechanical Pulp Sheet Properties 1279

5.4 Optical Properties of Laboratory Sheets 1279

6 Papermaking Properties of Pulps 1281

6.1 Beating 1281

6.2 Drainage Resistance 1281

6.3 Drainage (Dewatering) Time 1283

6.4 Aging 1284

6.4.1 Accelerated Aging 1284

Index 1291

XXII Contents

XXIII

Дата добавления: 2015-10-21