vol5 mechanical pulping...mechanical pulping papermaking science and technology a book series...
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Mechanical Pulping
Papermaking Science and Technologya book seriescovering the latesttechnology andfuture trends
Book 5
Second Edition
Totally updated version
Book editorBruno Lönnberg, D.Sc. (Tech.), Professor (emeritus), Åbo Akademi University
PublisherPaper Engineers’ Association/Paperi ja Puu Oy
Paperi ja Puu Oy
8
Table of Contents1 Introduction............................................................................................................................9
2 Idea of mechanical pulping .................................................................................................17
3 History of mechanical pulping ............................................................................................23
4 Fundamentals of mechanical pulping.................................................................................35
5 Wood raw materials .............................................................................................................68
6 Grinding and pressure grinding ........................................................................................116
7 Thermomechanical pulping ...............................................................................................174
8 Chemimechanical pulping .................................................................................................247
9 Screening and cleaning .....................................................................................................282
10 Reject refining ....................................................................................................................327
11 Bleaching of mechanical pulps .........................................................................................360
12 Thickening, storage and post-refining .............................................................................399
13 Flowsheets for various mechanical pulping and screening processes ..........................419
14 Environmental impacts of mechanical pulping ................................................................430
15 The character and properties of mechanical pulps .........................................................456
16 Future outlook ....................................................................................................................515
Conversion factors .............................................................................................................535
Index ...................................................................................................................................537
9
CHAPTER 1 Introduction
Contents of the book1 ...........................................................................................................10
How to interpret the data2 ....................................................................................................11
Abbreviations3 used ..............................................................................................................12
17
CHAPTER 2 Idea of mechanical pulping
Wood for mechanical pulping1 .............................................................................................18
Wood treatments in mechanical pulping 2 ...........................................................................18
Brief description of the mechanical pulping3 ......................................................................20
Characteristics of mechanical pulps4 ..................................................................................21
End uses of mechanical pulps5 ............................................................................................22
23
CHAPTER 3 History of mechanical pulping
Invention of the grinding process1 .......................................................................................24
Development of the grinding process2 .................................................................................25
First commercial grinders2.1 ......................................................................................................25
First reject refiner2.2 ..................................................................................................................28
Brown groundwood and chemigroundwood processes2.3 ...........................................................28
Hot grinding process2.4 ..............................................................................................................28
Grindstone development2.5 ........................................................................................................28
Development of main grinder types2.6 ........................................................................................29
Pressure grinding (PGW)2.7 ........................................................................................................29
Thermomechanical pulping (TMP)3 ......................................................................................30
Groundwood reject refining3.1 ....................................................................................................30
Original thermomechanical pulping process for hardboards3.2 ...................................................30
Development of RMP for printing papers3.3 ................................................................................31
Development of modern TMP3.4 .................................................................................................32
Novel methods to produce mechanical pulps4 ....................................................................33
Development of testing methods5 ........................................................................................33
References ............................................................................................................................34
35
CHAPTER 4 Fundamentals of mechanical pulping
Rheological behaviour of wood 1 ..........................................................................................36
Fundamental mechanisms in mechanical pulping, especially grinding 2 ..........................40
Principles of defibration of wood by grinding2.1 ..........................................................................40
Breakdown of the fibre structure by fatigue 2.1.1 ...............................................................41
Removal of fibres from wood by peeling action 2.1.2 .........................................................43
Wood structure parameters affecting the breakdown process2.2 ................................................44
Thin-/thick-walled fibres2.2.1 ............................................................................................45
Layer structure of the fibre 2.2.2 ........................................................................................45
Wood, a viscoelastic composite polymer2.2.3 .....................................................................45
Main physical parameters affecting wood grinding2.3 .................................................................46
Wood in a cyclic stress field 2.3.1 ......................................................................................46
Influence of amplitude, frequency and temperature2.3.2 ....................................................47
Energy consumption in grinding 2.4 ............................................................................................51
Fundamental mechanisms in refining 3 ...............................................................................52
Development of fibre properties during refining3.1 ......................................................................53
Traditional descriptions of refining3.2 ..........................................................................................53
Theoretical approaches to understanding refining3.3 ..................................................................54
Measured data from the plate gap3.4 .........................................................................................55
Present knowledge and understanding of the fundamentals in refining3.5 ..................................57
Reasons for differences in energy consumption between grinding and refining 4 ............58
Energy consumption in grinding and refining4.1 ..........................................................................58
Reasons for high energy consumption4.2 ....................................................................................58
Reasons for high energy consumption in chip refining4.3 ............................................................59
References ............................................................................................................................62
68
CHAPTER 5 Wood raw materials
General wood properties1 .....................................................................................................70
Wood basic density1.1 ................................................................................................................71
Wood moisture content1.2 ..........................................................................................................72
Juvenile wood1.3 ........................................................................................................................74
Heartwood1.4 .............................................................................................................................74
Unsuitable parts of the wood raw material1.5 .............................................................................75
Wood species used in mechanical pulping2 ........................................................................78
Wood and fibre characteristics2.1 ...............................................................................................79
Softwoods: spruces and pines2.1.1 ....................................................................................79
Hardwoods: poplars and eucalyptus2.1.2 ...........................................................................80
Properties of thermomechanical pulps2.2 ...................................................................................82
Softwoods2.2.1 ..................................................................................................................82
Hardwoods2.2.2 .................................................................................................................84
Properties of groundwood pulps2.3 .............................................................................................84
Softwoods2.3.1 ..................................................................................................................85
Hardwoods2.3.2 .................................................................................................................88
Variations in properties between trees3 ...............................................................................90
Genetic control of wood properties3.1 .........................................................................................90
Within-tree property variation 3.2 ................................................................................................91
Fibre length3.2.1 ................................................................................................................92
Fibre width3.2.2 .................................................................................................................93
Cell wall thickness3.2.3 .....................................................................................................94
Cross-sectional cell wall area3.2.4 .....................................................................................96
Microfibril angle3.2.5 .........................................................................................................96
Within-stand variation3.3 ............................................................................................................97
69
Wood raw materials
Pulp properties of different wood assortments4 ..................................................................98
Pulpwood vs. sawmill chips4.1 ...................................................................................................99
Butt log vs. top log4.2 ...............................................................................................................102
Heartwood vs. sapwood4.3 .......................................................................................................103
Slow-grown vs. fast-grown wood4.4 .........................................................................................103
Seasonal variations in wood properties5 ...........................................................................104
Effect of wood supply practices on wood properties6 .......................................................105
Effect of wood handling operations on wood and chip properties7 ..................................106
References ..........................................................................................................................109
116
CHAPTER 6 Grinding and pressure grinding
Introduction1 ........................................................................................................................118
Grinder productivity2 ...........................................................................................................119
Two-pocket wood grinders for groundwood processes3 ..................................................121
Tampella two-pocket atmospheric SGW grinder3.1 ...................................................................121
Metso atmospheric SGW grinder3.2 ..........................................................................................121
Montague two-pocket SGW grinder3.3 ......................................................................................123
Metso pressure grinders3.4 ......................................................................................................124
Continuous Metso two-pocket grinder3.5 ..................................................................................128
Wood grinding processes4 ..................................................................................................128
Atmospheric groundwood (SGW)4.1 ..........................................................................................128
Pressure groundwood processes4.2 ..........................................................................................129
PGW95 process4.2.1 ........................................................................................................132
PGW70 process4.2.2 ........................................................................................................134
PGW-S120 process4.2.3 ..................................................................................................135
Chain grinders and thermogroundwood (TGW)5 ................................................................136
Grindstones and grindstone treatments6 ...........................................................................140
Ceramic grindstones6.1 ............................................................................................................140
Abrasive specifications and their influence on grindstone behaviour6.2 .....................................141
New grinding surfaces6.3 .........................................................................................................143
Grindstone treatments6.4 .........................................................................................................143
Burr treatments for grindstones6.5 ...........................................................................................144
Grindstone truing6.5.1 .....................................................................................................145
Grindstone sharpening6.5.2 .............................................................................................145
Dulling of grindstone6.5.3 ................................................................................................146
Grindstone grooving6.5.4 .................................................................................................146
117
Grinding and pressure grinding
Grindstone surface control with ultra-high-pressure water6.6 ...................................................147
Water jet equipment6.6.1 .................................................................................................149
Grindstone treatment with water jet6.6.2 .........................................................................149
Impacts of water jet conditioning on grinding process variables and pulp properties6.6.3 149
Water Jet Control system6.6.4 .........................................................................................151
Grinder feeding systems7 ...................................................................................................151
Feeding system for chain grinders7.1 .......................................................................................152
Charging system for pocket grinders7.2 ....................................................................................153
Grinding control8 .................................................................................................................155
Control requirements8.1 ...........................................................................................................155
Grinding from a control viewpoint8.2 .........................................................................................156
Grinding process8.3 ..................................................................................................................156
Hierarchy of grinding controls8.4 ..............................................................................................158
Surface wear compensation8.4.1 .....................................................................................158
Batch control8.4.2 ............................................................................................................159
Grinding control strategy8.5 ......................................................................................................161
Grinder group control strategy8.5.1 ..................................................................................161
Optimum operating point strategy8.5.2 ............................................................................163
Water Jet Control8.5.3 .....................................................................................................163
PGW pulps and various paper grades9 ...............................................................................164
Pulp properties9.1 .....................................................................................................................165
Suitability for various paper grades9.2 ......................................................................................166
References ..........................................................................................................................169
174
CHAPTER 7 Thermomechanical pulping
Introduction to thermomechanical pulping1 ......................................................................176
Principles of refiner mechanical pulping1.1 ...............................................................................176
Main refiner types1.2 ................................................................................................................177
Thermomechanical pulping process1.3 .....................................................................................177
Energy consumption and yield1.4 .............................................................................................178
Handling and pretreatment of chips2 .................................................................................179
Chip washer2.1 .........................................................................................................................180
Dewatering of chips2.2 .............................................................................................................181
Chip wash water system2.3 ......................................................................................................181
Chip preheating2.4 ...................................................................................................................182
Chip impregnation systems 2.5 .................................................................................................183
Disc refiner3 .........................................................................................................................186
Refiner concepts of different manufacturers3.1 .........................................................................186
Single-disc (SD) refiners3.2 ......................................................................................................186
Andritz SB 150 and 170 single-disc refiners3.2.1 .............................................................186
Metso RGP SD single-disc refiners3.2.2 ...........................................................................188
Other single-disc refiners: SD 65 and HXD643.2.3 ...........................................................189
High-capacity TMP refiners3.3 ..................................................................................................192
Metso RGP CD refiner3.3.1 ...............................................................................................192
Andritz Twin refiner3.3.2 ..................................................................................................194
Double disc (DD) refiners3.4 .....................................................................................................196
Processing pulp and steam in the refiner line3.5 .......................................................................198
Refining conditions and design parameters3.6 ..........................................................................202
Refiner segments — the “heart” of the refining process4 ................................................204
Refiner segment design4.1 .......................................................................................................206
Materials of refiner segments4.2 ...............................................................................................208
175
Thermomechanical pulping
Main TMP process types5 ...................................................................................................209
“Standard” TMP line5.1 ............................................................................................................209
Single-stage refining5.2 ............................................................................................................213
Energy-saving TMP processes5.3 .............................................................................................214
High-speed and high-intensity TMP refining5.3.1 .............................................................215
Chip pretreatment5.3.2 ....................................................................................................217
Third-stage post-refining5.3.3 .........................................................................................218
Energy savings with refiner plate development5.3.4 .........................................................218
Refiner type and process conditions and their impact on pulp properties6 .....................221
Intensity of refining6.1 ..............................................................................................................221
Influence of refiner type6.2 .......................................................................................................222
Refiner speed6.3 .......................................................................................................................223
Pulp consistency6.4 ..................................................................................................................224
Production rate6.5 ....................................................................................................................226
Preheating and steaming of chips6.6 ........................................................................................226
Temperature in preheating and refining6.7 ................................................................................228
Process control7 ..................................................................................................................229
Control requirements7.1 ...........................................................................................................229
Basic controls7.2 ......................................................................................................................230
Plate gap control7.3 ..................................................................................................................231
Production rate7.4 ....................................................................................................................231
Refining consistency7.5 ............................................................................................................232
Refining pressures7.6 ...............................................................................................................232
Pulp quality control7.7 ..............................................................................................................233
Heat recovery8 .....................................................................................................................234
Amount and composition of TMP steam8.1 ...............................................................................234
Reboiler for condensing TMP steam and generating clean steam8.2 .........................................236
Auxiliary heat exchangers8.3 ....................................................................................................236
Start-up scrubber for TMP steam8.4 .........................................................................................238
Surface condenser for low-pressure TMP steam8.5 ..................................................................238
Turpentine recovery8.6 .............................................................................................................240
Heat recovery as a part of the low-pressure steam net 8.7 .......................................................242
References .........................................................................................................................243
247
CHAPTER 8 Chemimechanical pulping
Introduction1 ........................................................................................................................248
Process alternatives2 ..........................................................................................................249
Position of the chemical treatment stage in the process2.1 .......................................................249
Type of chemical treatment2.2 ..................................................................................................250
Chemical stage3 ..................................................................................................................251
Sulphonation chemistry3.1 .......................................................................................................252
Effect of process variables on the sulphonate content3.2 ..........................................................254
The mechanical stage4 .......................................................................................................255
Dynamic mechanical properties of chemically treated wood and fibres4.1 ................................257
Kind of rupture at fiberising4.2 ..................................................................................................257
Process design and operation5 ...........................................................................................258
General schemes5.1 .................................................................................................................258
Chemical pretreatment5.2 ........................................................................................................260
Refining5.3 ...............................................................................................................................262
Drying5.4 ..................................................................................................................................263
Baling5.5 ..................................................................................................................................264
Special processes6 ..............................................................................................................265
Interstage sulphonation6.1 ........................................................................................................265
Reject sulphonation6.2 .............................................................................................................265
Chemical treatment with alkaline peroxide6.3 ...........................................................................266
APMP process6.3.1 ..........................................................................................................267
P-RC APMP process6.3.2 .................................................................................................268
Alkaline peroxide treatment of reject6.4 ....................................................................................268
Ozone treatment6.5 ..................................................................................................................269
Fibre and pulp properties7 ..................................................................................................270
Fibre properties7.1 ....................................................................................................................270
Pulp properties7.2 .....................................................................................................................271
End uses8 .............................................................................................................................275
Market pulps9 ......................................................................................................................276
References ..........................................................................................................................278
282
CHAPTER 9 Screening and cleaning
Background 1 .......................................................................................................................284
Principle and objectives of screening1.1 ...................................................................................284
Screening and fractionation1.1.1 ......................................................................................286
Screening principle – barrier and probability screening1.1.2 ............................................287
Design of a pressure screen2 ..............................................................................................288
Ge2.1 neral construction ............................................................................................................288
Feed arrangement2.2 ................................................................................................................290
Screen basket geometry2.3 ......................................................................................................290
Rotor design2.4 ........................................................................................................................291
Flows within the screen3 ....................................................................................................292
Axial flow in screen basket and reject removal3.1 .....................................................................292
Radial flow in screen basket3.2 ................................................................................................293
Tangential flow in screen basket3.3 ..........................................................................................293
Flow near basket surface and apertures3.4 ...............................................................................294
Turbulence, pulsation and backflow3.5 .....................................................................................294
Characterisation of screening and fractionation4 .............................................................296
Basic equations4.1 ...................................................................................................................296
Screening efficiencies4.2 ..........................................................................................................298
Assessment of performance with operating curves4.3 ..............................................................299
Parameters affecting pressure screen performance 5 ......................................................300
Design parameters5.1 ...............................................................................................................300
Rotor design5.1.1 .............................................................................................................301
Screen basket geometry5.1.2 ..........................................................................................302
Operating parameters5.2 ..........................................................................................................304
Furnish parameters5.3 ..............................................................................................................306
Energy consumption and power in pressure screening 6 .................................................306
283
Screening and cleaning
Screening systems7 ............................................................................................................308
Main-line screening of SGW and PGW7.1 ..................................................................................309
Main-line screening of TMP and CTMP7.2 .................................................................................310
Screening of rejects7.3 .............................................................................................................311
Control of screening8 ..........................................................................................................312
Control of a single screen8.1 .....................................................................................................312
Control of parallel screens and screens in series8.2 ..................................................................313
Control of two-stage screening 8.3 ...........................................................................................314
Control of multi-stage screening 8.4 .........................................................................................314
On-line pulp quality measurements and control of screening8.5 ...............................................314
Cleaning and sand removal9 ...............................................................................................316
Theory 9.1 ................................................................................................................................316
Cleaner types 9.2 ......................................................................................................................318
Cleaning systems 9.3 ................................................................................................................319
Sand removal 9.4 ......................................................................................................................319
Control of cleaning 9.5 ..............................................................................................................321
References ..........................................................................................................................322
327
CHAPTER 10 Reject refining
Fibres, equipment and systems1 ........................................................................................328
Reject handling2 ..................................................................................................................329
Thickening2.1 ...........................................................................................................................329
Bow screen2.1.1 ..............................................................................................................330
Screw press2.1.2 .............................................................................................................330
Twin-roll press2.1.3 .........................................................................................................331
Twin-wire press2.1.4 .......................................................................................................333
Pretreatment2.2 ........................................................................................................................334
Reject refiners3 ....................................................................................................................335
Reject refining systems3.1 ........................................................................................................338
Control and operating principles4 ......................................................................................341
Main and control variables4.1 ...................................................................................................342
Process conditions and disturbances 4.2 ..................................................................................344
HC refining4.2.1 ...............................................................................................................347
LC refining4.2.2 ...............................................................................................................349
Effects of reject refining on pulp and paper properties 5 ..................................................350
Printing paper grades 5.1 ..........................................................................................................354
Board grades5.2 .......................................................................................................................355
Hardwood CTMP5.3 ..................................................................................................................355
References ..........................................................................................................................357
360
CHAPTER 11 Bleaching of mechanical pulps
Bleaching or brightening1 ...................................................................................................362
Factors affecting the brightness of high-yield pulps2 .......................................................362
Principles of bleaching high-yield pulps3 ..........................................................................366
Peroxide bleaching4 ............................................................................................................367
Reactions4.1 .............................................................................................................................367
Process variables4.2 .................................................................................................................368
Peroxide dose4.2.1 ..........................................................................................................368
Removal of transition metal ions 4.2.2 .............................................................................369
Pulp pH 4.2.3 ...................................................................................................................370
Stabilising agents4.2.4 .....................................................................................................373
Consistency4.2.5 .............................................................................................................375
Temperature4.2.6 ............................................................................................................376
Retention time 4.2.7 .........................................................................................................376
Acidification 4.2.8 ............................................................................................................376
Bleach plant design and operation4.3 .......................................................................................377
Single-stage medium-consistency bleaching4.3.1 ............................................................377
High-consistency bleaching4.3.2 ......................................................................................378
Medium- and high-consistency peroxide bleaching4.3.3 ..................................................379
Refiner bleaching4.3.4 .....................................................................................................381
Flash dryer bleaching4.3.5 ...............................................................................................381
Dithionite (hydrosulphite) bleaching5 ................................................................................381
Reactions5.1 .............................................................................................................................381
Process variables 5.2 ................................................................................................................383
Dithionite (hydrosulphite) dose 5.2.1 ................................................................................383
Chelating agents5.2.2 ......................................................................................................384
Pulp pH 5.2.3 ...................................................................................................................384
361
Bleaching of mechanical pulps
Consistency 5.2.4 ............................................................................................................384
Temperature 5.2.5 ...........................................................................................................385
Retention time5.2.6 ..........................................................................................................385
Bleach plant design and operation5.3 .......................................................................................385
Tower bleaching5.3.1 .......................................................................................................385
Two-stage bleaching with peroxide and dithionite5.3.2 ....................................................385
Chest bleaching5.3.3 .......................................................................................................387
Refiner and grinder bleaching5.3.4 ..................................................................................387
Other bleaching chemicals6 ................................................................................................388
Potential bleaching chemicals6.1 ..............................................................................................388
Sodium bisulphite6.2 ................................................................................................................388
Formamidine sulphinic acid6.3 .................................................................................................389
Bleaching of chemimechanical pulps7 ...............................................................................389
Brightness reversion8 .........................................................................................................390
General8.1 ................................................................................................................................390
Determination of brightness reversion8.2 ..................................................................................391
Thermal brightness reversion8.3 ...............................................................................................392
Light-induced brightness reversion8.4 ......................................................................................393
Effect on yield and papermaking properties9 ....................................................................393
Dithionite (hydrosulphite) bleaching9.1 .....................................................................................393
Peroxide bleaching9.2 ...............................................................................................................394
Development of the bleaching technologies 10 ...................................................................395
References ..........................................................................................................................396
399
CHAPTER 12 Thickening, storage and post-refining
Thickening1 .........................................................................................................................400
Disc filters1.1 ...........................................................................................................................400
Broke deckers1.2 ......................................................................................................................402
Bow screens 1.3 .......................................................................................................................402
Screw presses, twin-roll presses and twin-wire presses1.3.1 ..........................................403
Storage of mechanical pulps2 ............................................................................................404
Storage systems2.1 ..................................................................................................................404
Effect of storage on pulp properties2.2 ......................................................................................405
Post-refining 3 .....................................................................................................................406
Objectives of post-refining3.1 ...................................................................................................406
Equipment and process systems 3.2 .........................................................................................407
Refining conditions and operations3.3 .......................................................................................408
Refining effects3.4 ....................................................................................................................413
References ..........................................................................................................................418
419
CHAPTER 13 Flowsheets for various mechanical pulping and screening processes
Groundwood and thermomechanical pulping processes1 ................................................420
SGW and PGW pulp screening processes1.1 .............................................................................422
TMP and CTMP pulp screening processes1.2 ............................................................................422
Mechanical pulping processes for newsprint-paper grades 2 ..........................................422
Newsprint-grade PGW pulp screening processes2.1 .................................................................423
Newsprint-grade TMP pulp screening processes2.2 ..................................................................424
Mechanical pulping processes for SC- and LWC-paper grades3 ......................................425
SC- and LWC-grade SGW and PGW pulp screening processes3.1 ..............................................425
SC- and LWC-grade TMP pulp screening processes3.2 .............................................................426
Mechanical pulping processes for board grades4 .............................................................427
Board-grade SGW and PGW pulp screening processes4.1 .........................................................428
Board-grade TMP and CTMP pulp screening processes4.2 ........................................................428
References ..........................................................................................................................429
430
CHAPTER 14 Environmental impacts of mechanical pulping
Woodyard, debarking, pulping and bleaching processes1 ................................................432
Emissions from processes2 ................................................................................................433
Wood and chip storage3 ......................................................................................................435
Trends in techniques3.1 ............................................................................................................435
Changes in wood during storage3.2 ..........................................................................................435
Debarking and chipping4 ....................................................................................................436
Wet and dry debarking4.1 .........................................................................................................436
Water circulation systems in debarking4.2 ................................................................................436
Need for water 4.3 ....................................................................................................................437
Treatment of 5 debarking effluent .......................................................................................437
Composition and concentration of debarking circulation water5.1 .............................................437
Effluent load5.2 .........................................................................................................................438
Release of wood components into water in mechanical pulping and bleaching6 ...........438
Discharge data for different pulping processes6.1 .....................................................................438
Influence of bleaching stages6.2 ...............................................................................................439
Chemical character of released wood components6.3 ...............................................................440
Toxic components in effluents6.4 ..............................................................................................443
Factors influencing release of wood components into water7 ..........................................443
Effect of pulping conditions7.1 ..................................................................................................443
Effects of wood quality7.2 .........................................................................................................444
Evaporation of compounds in mechanical pulping8 ..........................................................445
Volatility of wood compounds8.1 ...............................................................................................445
Contents of volatile compounds8.2 ...........................................................................................445
Water circulation systems9 in mechanical pulping plants ................................................446
Connection between pulp mill and paper mill9.1 .......................................................................446
Washing stage9.2 .....................................................................................................................447
431
Environmental impacts of mechanical pulping
Treatment of mechanical pulping effluents10 ......................................................................448
Purification methods10.1 ............................................................................................................448
Potential for installing internal cleaning stages in a mechanical pulp plant10.2 ...........................449
Zero effluent technology10.3 ......................................................................................................449
Carbon footprint of a mechanical printing paper11 .............................................................450
References ..........................................................................................................................452
456
CHAPTER 15 The character and properties of mechanical pulps
Origin of mechanical pulp properties 1 ..............................................................................458
Mechanical pulp properties and paper/board grades2 ......................................................461
Mechanical printing papers2.1 ..................................................................................................461
Newsprint 2.1.1 ...............................................................................................................464
SC paper2.1.2 ..................................................................................................................465
LWC paper2.1.3 ...............................................................................................................466
Mechanical-pulp board2.2 ........................................................................................................466
Development of pulp properties3 ........................................................................................467
Fibre shortening3.1 ...................................................................................................................467
Fibre-wall thickness and structure3.2 .......................................................................................468
Pulp fractions and fibre properties3.3 ........................................................................................469
Long-fibre fraction3.3.1 ...................................................................................................470
Middle fraction3.3.2 .........................................................................................................470
Fines fraction3.3.3 ...........................................................................................................471
Properties of fractions for pulp characterisation3.3.4 ........................................................474
Latency in mechanical pulps3.4 ................................................................................................476
Mechanical pulp fibres and paper recycling3.5 ..........................................................................476
Properties of pulp suspensions and their characterisation4 .............................................478
Pulp property versus method4.1 ...............................................................................................478
Methods for determining drainability4.2 ....................................................................................479
Canadian Standard Freeness, Schopper-Riegler value and drainage time4.2.1 .................479
Water retention value4.2.2 ...............................................................................................480
Specific filtration resistance, specific surface area and settling rate4.2.3 .........................480
Water quality and its effect on drainage4.2.4 ...................................................................481
Methods for determining fractional composition4.3 ...................................................................482
Methods for determining shive content4.4 ................................................................................485
Methods for determining fines properties4.5 .............................................................................486
457
The character and properties of mechanical pulps
Fibre properties and characterisation methods 5 ..............................................................488
Fibre property versus method5.1 ...............................................................................................488
Methods for determining fibre dimensions5.2 ...........................................................................489
Fibre length5.2.1 ..............................................................................................................489
Fibre form5.2.2 ................................................................................................................491
Cross-sectional dimensions of fibres5.2.3 ........................................................................492
Methods for determining fibre coarseness5.3 ...........................................................................494
Methods for determining fibre wall structure5.4 ........................................................................495
Fibre wall damage5.4.1 ....................................................................................................495
Internal fibrillation5.4.2 ....................................................................................................496
Fibre wall dimensions along the fibre length axis 5.4.3 .....................................................497
Flexibility and stiffness of fibres5.4.4 ...............................................................................498
Methods for determining fibre surface properties5.5 .................................................................498
External fibrillation5.5.1 ...................................................................................................498
Fibre surface roughness5.5.2 ...........................................................................................499
Chemical composition of fibre surfaces5.5.3 ....................................................................500
Handsheet properties6 and paper testing .........................................................................501
Preparation of handsheets6.1 ...................................................................................................501
Handsheets for testing physical properties except optical properties 6.1.1 .......................501
Handsheets for testing optical properties6.1.2 ..................................................................502
Testing of handsheet properties 6.2 ..........................................................................................502
Typical sheet properties of mechanical pulps6.3 .......................................................................503
References ..........................................................................................................................505
515
CHAPTER 16 Future outlook
Future demand for mechanical pulps 1 ..............................................................................516
Development of paper demand 2010–20201.1 .........................................................................516
Furnish trends1.2 ......................................................................................................................518
Production of mechanical pulps1.3 ...........................................................................................520
Future consumption of mechanical pulps1.4 .............................................................................522
Paper and mechanical pulp quality development 2 ...........................................................522
General quality characteristics 2.1 ............................................................................................522
Newsprint2.2 ............................................................................................................................522
Supercalendered (SC) papers2.3 ...............................................................................................523
Coated mechanical and coated wood-free papers2.4 ................................................................523
Carton boards2.5 ......................................................................................................................523
Energy consumption of GW and TMP3 ................................................................................524
General trends3.1 .....................................................................................................................524
Possibilities to reduce specific energy consumption3.2 .............................................................524
Consequences of electric energy savings3.3 .............................................................................526
Impact of the increasing use of recycled fibre 4 ................................................................527
Raw material availability 5 ..................................................................................................528
Process development 6 .......................................................................................................530
Pulping capacity development 6.1 .............................................................................................530
Advantages and disadvantages of various mechanical pulping processes6.2 ............................531
SWOT analysis for mechanical pulping 6.3 ................................................................................531
References ..........................................................................................................................533