paper machine design and operation

"Paper Machine Design andOperation--Descriptions and

Explanations"By Gunnar Gavelin

1998., 222 pp., Published by Angus WildeItem Number: 08AWPMDISBN: 0-9694628-2-4

This new book offers an update on current paper machine developments and operatingpractices and compares design approaches by major paper equipment manufacturers.Seven chapters cover the following topics: Approach Flow, Headboxes, Fourdrinier WetEnd, Twin Wire Formers, Press Section, Drying of Paper, Surface Treatment of Paper.

TABLE OF CONTENTS

PREFACE vii

ACKNOWLEDGEMENTS viii

CHAPTER 1 -- APPROACH FLOW

1.1 Introduction – Basics of Papermaking 11.2 Definitions and Nomenclature 21.3 White Water System 3

Short Circulation 3Long Circulation 5

1.4 Machine Refiners 51.5 Stuff Box 51.6 Basis Weight Valve 61.7 Basis Weight Variations 61.8 Fan Pump 71.9 Headbox Feed Pump 81.10 Centricleaners 81.11 Deaeration 81.12 Screens 10

References 12

CHAPTER 2 – HEADBOXES

2.1 Headbox With Air Cushion 13Flow Spreader 14Flow Distributor 14Headbox Proper 15Perforated Rolls 15Air Cushion 17

2.2 Hydraulic Headbox 182.3 Slice 19



2.4 Acceleration of Flow in the Headbox 202.5 Fiber Angle 212.6 Dilution Control 22

Voith Module Jet 23Beloit System 25Valmet system 26

2.7 Precision Demands on Headbox Surfaces 282.8 Hydraulic Headbox Developments 28

Beloit converflo 302.9 Multichannel Headbox 32

Why Multichannel Headboxes? 342.10 Headbox Effects on formation

and MD/CD Ratio 352.11 Length of the Free Jet 352.12 Efflux Ratio 352.13 Automation of Headbox Operation 37

References 38

CHAPTER 3 – FOURDRINIER WET END

3.1 Fourdrinier Components 40Breast Roll 41Deckle Rulers 41Forming Board 41Table Rolls 42Foils (Foil blades) 42Wet Suction Boxes 44Dry Suction Boxes 44Dandy Roll 45Couch Roll 47Couch Press 48Wire Turning Roll 49

3.2 Closed Transfer 493.3 Forming Fabric 50

Fabric Designs 50Seaming 51Fabric Quality 52

3.4 Auxiliary Rolls 54Guide and Stretch Rolls 54Bowed Roll 56

3.5 Fabric Cleaning 58High Pressure Showers 58Voith Jetcleaner 60

3.6 Drainage Along the Wire Table 613.7 Elements of the White Water System 62

Dry Suction Box Seal Pit 62Wire Pit 63White Water Tanks 63



White Water Cleaning 643.8 Broke System 66

Couch Pit 66Dry Broke 67

3.9 Wire Retention 683.10 White Water system Closure-

Reducing Fresh Water Usage 693.11 Cleaning of Paper Mill Effluent 70

References 71

CHAPTER 4 – TWIN-WIRE FORMERS

4.1 Blade Former 73Drainage Process on a Blade Former 74

4.2 Roll Former 75Drainage Process on a Roll Former 75

4.3 Hybrid Former 77Valmet Sym-Former 77Beloit Bel Bond 79Voith DuoFormer D 80

4.4 Roll-blade Former 814.5 New Blade Forming Technology 824.6 Geometry of the Entering Nip 82

Problems of Two-Sidedness 844.7 Description of Specific Formers 84

Valmet Speed Former 85Valmet Speed Former MB 86

4.8 Speed Former and Paper Quality 874.9 Blade-Roll Former 884.10 Description of Specific Formers 88

Bel Baie III 88Bel Baie IV 90Voith DuoFormer CFD 91

4.11 Horizontal Gap Former 944.12 Forming Fabrics 954.13 Theory of Two-Sided Drainage 954.14 Forming Unit Alternatives 96

Membranes in the Slice Area 96Optimization of Roll Drainage 97Blade Section Drainage 97

4.15 Paper Quality Considerations 984.16 High-Consistency Forming 994.17 Paperboard Machine Formers 1014.18 Tissue Machine Formers 103

Valmet “C-Wrap” 103



Valmet Crescent Former 104Valmet Performer Noveau 104

References 105

CHAPTER 5 – PRESS SECTION

5.1 The Process of Pressing 106Rewetting Problem 107

5.2 Plain Press 1075.3 Suction Press 108

Other Suction Roll Applications 109Suction Roll Shells 109Roll Shell Covers 110

5.4 Grooved Press 112Grooved Steel Roll 112Grooved Press Geometry 113

5.5 Blind-Drilled Press 1145.6 Fabric Press 1145.7 Long-Nip Press 1155.8 Large-Roll Press 1165.9 Shoe Press 116

Design Principle 116Effect of Shoe Pressing on Paper Quality 118Press Sections With Shoe Presses 119

5.10 Double-Felted Press 1225.11 Types of Rolls 123

Antideflection (Controlled Crown) Rolls 123Granite Rolls 125Composite-Covered Rolls 126Peeler Rolls 126

5.12 Examples of Press Sections 127Two-Nip Press Sections 127Three-Nip Press Sections 127Fourth Nip 129

5.13 Pressing at High Temperature 130Steam Boxes 130Hot Presses 131

5.14 Open-Draw Presses 134Theory and Practice of Open Draws 135

5.15 Closed Transfer – Press Section to Dryers 1375.16 Economics of Pressing 1375.17 Press Felts 138

Felt Construction 138Performance Requirements 139



Seamed Press Felts 139Felt Suction Boxes 140High-Pressure Showering 140Cost of Paper Machine Clothing 140

5.18 Vacuum Pumps 140Water-Ring Vacuum Pump 140Water-Ring Pump Heat Recovery 141Turbo Compressor 142

5.19 Pressing and Paper Quality 143Shadow Marking 143

5.20 Future Development of Pressing 143References 147

CHAPTER 6 – DRYING OF PAPER

6.1 Cylinder Drying 149Heat Transfer Considerations 149

Process Considerations 1506.2 Yankee Cylinder and MG Cylinder Drying 151

Yankee and MG Hoods 1526.3 Multicylinder Drying 1536.4 Steam and Condensate Systems 155

Condensate Behavior 156Turbulence Generators 159Condensate Dams 160Condensate Removal 160Blow-Through Steam 160Control of Steam and Condensate Flows 162

6.5 Syphon Designs 166Rotating Syphons 166Stationary Syphons 167Syphon for Yankee Dryer 168Syphon Dimensions 169

6.6 Dryer Fabrics 170Air Permeability 170Cleaning 171

6.7 Multicylinder Drying – Ventilation 1726.8 Sheet Flutter and Closed Sheet Transfer 1746.9 New Multicylinder Dryer Designs 176

Beloit 178Valmet 178Voith 180

6.10 Effect of Closed Transfer on Sheet Shrinkage 1816.11 Steam Consumption 182



6.12 Hood Ventilation 183Heat Recovery 183Hood Air Humidity Control 184Hood Air Humidity Control 185The Dew Point 186Variable Speed Fans 187Scrubber for Exhaust Air 188

6.13 Other Types of Paper Drying Systems 188Air Impingement Drying 188Drying with Hot Air 190Through Drying 191Infrared Drying 192Impulse Drying 192Condebelt Process 194

6.14 Drying and Paper Quality 1956.15 Control of MD and CD Moisture Profiles 197

References 197

CHAPTER 7 – SURFACE TREATMENT OF PAPER

7.1 Smoothing Press 1997.2 Breaker Stack 199

Pre-Calendar 2007.3 Size Press 200

Traditional Size Press 200Film Size Press 202

7.4 Conventional Hard-Nip Calender 206Cooling and Control 208

7.5 Soft Calender 209Soft Calendering Process 210Soft Calendering or Supercalendering? 212

7.6 Reel 2137.7 Paper Machine Drives 214

References 215

CREDITS 216

INDEX 218



INDEX

Aacceleration of headbox flow .................... 20-21air cushion headboxes ..............................13, 17air drying ...............................................190-191air impingement drying .........................188-190antideflection roll ...................................123-124approach flow .................................................. 4ash content, control of ..................................... 6auxiliary rolls ................................................. 54

Bbasis weight................................................. 2, 6

profile control ....................................... 19basis weight valve .................................6, 22-26basis weight variations.................................. 6-7Beloit,

Bel Baie III former ........................... 88-90Bel Baie IV former........................... 90-91Bel Bond former .............................. 79-80Converflo headbox.......................... 30-32dryer section .......................................178Extended Nip Press......................116-117TNT Reel ............................................212Ultra Rock press roll ............................126

blade former .................................................. 73blade former drainage............................... 74-75blade forming technology............................... 82blade section drainage................................... 93bowed rolls ............................................... 56-57breaker stack .........................................199-200breast roll ...................................................... 41broke system ............................................ 66-67

Ccalender

hard-nip........................................205-206soft...............................................208-211

calendering............................................205-212calender rolls,

cooling and control of ...................207-208centricleaners .................................................. 8ceramic press rolls........................................126closed transfer

press to dryers ....................................137within dryers.................................174-181

effect on shrinkage....................181-182wire to press......................................... 49

closing up the paper machine ........................ 69composite-covered press rolls ......................126condensate

behavior ...................................... 156-159dams .................................................. 160removal .............................................. 160systems ....................................... 160-166

controlled crown roll .............................. 123-124cost of papermachine clothing...................... 140couch pit .................................................. 66-67couch press.................................................... 48couch roll .................................................. 47-48cylinder drying....................................... 149-151

Ddandy roll .................................................. 45-46deaeration...................................................8-10deckle ruler .................................................... 41dew point in the hood ............................ 186-187dilution of stock before headbox....................3-5dilution control headboxes......................... 22-27

Beloit system................................... 25-26Valmet system...................................... 26Voith Module Jet.............................. 23-25

disc filter .................................................. 64-65doctor ........................................................ 111dominating fiber angle............................... 21-22drainage

blade section ........................ 74-75, 97-98on fourdrinier ................................... 61-62on roll formers ........................... 76-77, 97

draws .. ............................................... 135-136drives, paper machines ......................... 213-214dry broke handling.......................................... 67dryer designs, new ................................ 176-181dryer fabric............................................ 170-172

air permeability ............................ 170-171cleaning....................................... 171-172

dryer hooddew point control ......................... 185-187heat recovery............................... 183-184humidity control ........................... 185-187pressure control ........................... 184-185ventilation.................................... 183-187yankee................................................ 152

dryer sectioncascade ....................................... 160-163thermocompressor....................... 163-166

dryingair impingement........................... 188-190Condebelt .................................... 194-195cylinder........................................ 149-151hot air .......................................... 190-191impulse........................................ 192-194infrared............................................... 192multicylinder ................................ 153-155



temperature profile..............................155through................................................191yankee cylinder ............................151-152

drying and paper quality.........................195-197drying process .......................................150-151

ventilation ....................................172-174dry line .................................................... 44-45dry suction boxes...................................... 44-45

Eeconomics of pressing ...........................137-138effluent from paper mills ................................ 70efflux ratio ................................................ 35-37

Ffan pump ...................................................... 7-8felts (see press felts)fiber angle ...........................................21-22, 35flat boxes.................................................. 44-45flotation clarification.................................. 65-66foils ….. ............................................................. 42-43

formersBeloit Bel Baie III .......................74, 88-90Beloit Bel Baie IV ............................ 90-91Beloit Bel Bond ............................... 79-80for paperboarad machines............101-103for tissue machines ......................103-104gap........................................72-77, 81-82twin-wire.......................................... 72-94Valmet Crescent Former .....................104Valmet C-Wrap ...................................103Valmet Periformer Noveau..................104Valmet Speed Former ..................... 85-86Valmet Speed Former MB............... 86-87Valmet Sym-Former........................ 77-79Voith Duoformer CFD...................... 91-94Voith Duoformer CV............................. 88Voith Duoformer D .......................... 80-81

formers and paper quality ......................... 87-88forming

gapblade............................................ 73-75blade-roll ........................................... 88horizontal .......................................... 94roll................................................ 75-77roll-blade...................................... 81-82

high-consistency ............................99-100forming board ........................................... 41-42forming fabric ...........................50-54, 58-61, 95

cleaning .......................................... 58-59Voith jet cleaner ........................... 60-61

design ............................................. 50-51drainage capacity ................................. 53effect on paper quality.......................... 54fiber penetration ................................... 53

quality.............................................. 52-54seaming................................................ 51speed ................................................... 54stability ................................................. 53wear ..................................................... 52

forming roll................................................ 76-77forming shoe ............................................. 78-79fourdrinier forming section......................... 41-46

drainage profile................................ 61-62fresh water consumption ................................ 69

Ggranite roll ............................................. 125-126guide roll ................................................... 54-55

Hheadbox

air cushioned .................................. 13, 17automation of operation ................... 37-38effects on formation.............................. 35effects on MD/CD ration ....................... 35feed pump ...........................................7-8flow dilution for

basis weight control ...................... 22-27flow distributor ...................................... 14flowspreader ......................................... 14free jet length ....................................... 35hydraulic.......................................... 18-31membranes in slice......................... 30, 96multichannel .................................... 32-35perforated rolls ................................ 15-16slice................................................. 19-20surfaces demands ................................ 28surge tank............................................. 17

headbox proper .............................................. 15heat recovery

in drying....................................... 183-184vacuum pump.............................. 141-142

heat transfer equation .................................. 149high-pressure showers.........58-59. 140, 171-172horizontal gap formers ................................... 94hot pressing .......................................... 130-133hybrid former............................................. 77-79hydrogen bonding.............................................1

Iimpulse drying....................................... 192-194Isotuner (for fiber angle testing)...................... 21

Llong circulation.................................................5lumpbreaker roll ............................................. 47

Mmachine chest...............................................3-4



machine screens....................................... 10-11MD/CD ratio.........................................21-22, 35membranes in the slice area.....................30, 96MG cylinder ...........................................151-152moisture ratio................................................... 2moisture profile control .................................195multichannel headboxes ........................... 32-35multiply paperboard formers ..................101-103

Oopen draws ............................................134-136

Ppaperboard machines ............................101-103paper quality considerations

drying...........................................195-197forming process ................................... 54pressing ...............................118-119, 143

peeler rolls....................................................126perforated rolls in headboxes.................... 15-16pre-calender .................................................200presses

blind-drilled .........................................114double-felted ................................122-123fabric............................................114-115grooved........................................112-113hot ...............................................131-133large roll ..............................................116long nip ...............................................115open-draw ...........................................134plain ....................................................107shoe.............................................116-122smoothing ...........................................199suction .........................................108-109

press feltconstruction..................................138-139costs of ...............................................140high-pressure showering......................140performance requirements ..................139seaming ..............................................139

press felt suction boxes ................................140press impulse ...............................................115pressing

economy of .........................................137effect on paper quality..........118-119, 143future developments ....................143-146hot ...............................................130-133

press rollsantideflection................................123-125ceramic ...............................................126composite covered..............................126elastomeric covered.....................110-111granite.................................................125grooved...............................................112suction .........................................108-109

press sections

with shoe presses ........................ 119-122with two nips ....................................... 127with three nips ............................. 127-128with four nips ...................................... 129

profile controlbasis weight.......................................... 19moisture ............................................. 195

pulsation dampening ...................................... 17

Rreel ……................................................ 212-213refiner, machine ...............................................5rewetting in press nips.................................. 107roll-blade former........................................ 81-82roll former ................................................. 75-77roll former drainage............................. 76-77, 97

Sscreen plates.................................................. 11screens ..................................................... 10-11scrubber for dryer hood exhaust ............ 187-188shadow marking ........................................... 143sheet flutter ........................................... 173-174sheet shrinkage..................................... 181-182sheet transfer (see wet web transfer)shoe press............................................. 116-122

effect on quality ........................... 118-119principle....................................... 116-118

short circulation.............................................3-4single-felting for drying.......................... 175-181size press

film .............................................. 201-204traditional..................................... 200-201

slice …............................................................... .19-20slice bar .................................................... 19-20soft calender ......................................... 208-209soft calendering process........................ 209-212steam and condensate

flow control .................................. 162-163systems ............................... 160, 163-165

steam, blow-through.............................. 160-161steam boxes in pressing........................ 130-131steam economy in drying ...................... 182-183step diffusors (in headboxes)..................... 14-15stock flow control .............................................6stretch roll ................................................. 54-55stuff box...........................................................5suction boxes

dry ................................................... 44-45on press felts ...................................... 140wet ....................................................... 44

suction box seal pit................................... 45, 62suction press ......................................... 108-109suction rolls ........................................... 108-109suction roll shells................................... 109-111supercalendering................................... 211-212



surge tank...................................................... 17syphon (for condensate removal)

dimensions..........................................169rotating.........................................166-167stationary .....................................167-168yankee dryer ................................168-169

Ttable rolls....................................................... 42take-off angle (from press rolls) .............135-136thermo compressor dryer section...........163-165thermo roll (in calendering) ....................206-207through drying...............................................191tissue machine formers..........................103-104transfer belt ..........................................120, 137turbulence generator

in dryers .......................................159-160in headbox ........................................... 18

twin wire formers ...................................... 72-94two sided drainage, theory of ......................... 95two sidedness of paper,

problems of .......................................... 84

Vvacuum pumps

turbo compressor .........................142-143water ring .....................................140-141

ValmetCrescent Former .................................104C-Wrap Former...................................103impingement drying module .........189-190Optireel ........................................212-213Periformer Noveau..............................104Speed Former ................................. 85-86Speed Former MB........................... 86-87Sym-Flo headbox................................100Sym-Former.................................... 77-79Sym-Sizer ....................................201-202Vac Roll dryer section ..................178-180Valroc press roll ..................................126

Ventilationof dryer hoods ..............................183-187of dryer pockets ...........................172-174

ventilation fansvariable speed control .........................187

VoithDuoCleaner.........................................172Duoformer CFD............................... 91-93DuoFormer CV..................................... 88DuoFormer D .................................. 80-81DuoStabilizer dryer section..................180GR press roll .......................................126Jet cleaner ...................................... 60-61Module Jet ...................................... 23-25Top Duo Run dryer section...........180-181

Wwater ring vacuum pump....................... 140-141

heat recovery............................... 141-142web transfer

closed................................................. 137open ............................................ 134-136

wet suction box .............................................. 44wet web strength ...................................... 1, 135white water

cleaning, internal ............................. 64-66filters ............................................... 64-65flotation ........................................... 65-66system.................................................3-5system closure................................. 69-70tanks..................................................... 63

wire (see forming fabric)wire pit .......................................................... 63wire retention ................................................. 68wire turning roll............................................... 49

Yyankee cylinder ............................................ 151yankee hood ................................................ 152

paper machine design and operation

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