Pulp Bleaching Today

by Hans Ulrich Suess

Overview

This book describes the most effective application of chemicals in bleaching. It starts with a brief overview of the history of bleaching and then focuses on recent developments. The ban of chlorine from bleaching pulp has shifted bleaching to environmentally sound procedures. Elementary Chlorine Free bleaching (ECF bleaching) and Totally Chlorine Free bleaching (TCF bleaching) are explained. The potential of different bleaching chemicals is exemplified in detail with a special focus on what to do and what to avoid. Very recent knowledge about the sources of yellowing is utilized to explain the ideal strategy for the removal of chromophores and their precursors. Emphasis is placed on applicable bleaching, in clear contrast to sophisticated, complicated or simply expensive pseudo modern bleaching.

The target of this book is to explain the potential and the limitations of different chemicals and to demonstrate the necessity of comprehensive solutions for an environmentally sound use of the raw material wood, of chemicals, and of water in the production of pulp with top quality and yield.

This book

• should educate students in the art of bleaching,
• assist mill personal in their continuous effort for process optimization,
• help research and technology managers to successfully select their targets, and
• be on hand as reference of the most recent bleaching technology.

Product Details

ISBN-13:	9783110207378
Publisher:	De Gruyter
Publication date:	04/19/2010
Pages:	319
Product dimensions:	6.90(w) x 9.40(h) x 0.80(d)
Age Range:	18 Years

About the Author

Ulrich Suess , Evonik Degussa GmbH, Hanau-Wolfgang, Germany.

Table of Contents

1 Introduction 1

2 Brightening - a brief history 3

3 Bleaching agents, properties and generation 13

3.1 Oxidizing agents, physical and chemical properties 14

3.1.1 Oxygen 14

3.1.2 Chlorine dioxide 16

3.1.3 Hydrogen peroxide 22

3.1.4 Peracetic acid 27

3.1.5 Ozone 30

3.2 Reducing agents, physical and chemical properties 31

3.2.1 Sodium dithionite 31

3.2.2 Sulfur dioxide 34

3.2.3 Formamidine sulfinic acid (FAS) 35

3.3 Enzymes 36

3.4 Supporting chemicals in bleaching 37

3.4.1 Caustic soda, oxidized white liquor 37

3.4.2 Sodium silicate 39

3.4.3 Sulfuric acid 40

3.4.4 Chelating agents (sequestrants) 41

3.4.5 Magnesium sulfate (Epsom salt) 42

3.5 Risk and safety phrases 42

4 Bleaching of chemical Pulp 45

4.1 Bleaching stages and sequences 45

4.2 Oxygen delignification 53

4.2.1 Process conditions 57

4.2.2 Impact of poor washing 60

4.2.3 Oxygen delignification of hardwood pulp 64

4.2.4 Trouble shooting in oxygen delignification 66

4.3 Hot acid hydrolysis 68

4.4 Chlorine dioxide 73

4.4.1 Chlorine dioxide delignification 73

4.4.2 Chlorine dioxide in bleaching 83

4.4.3 Modified chlorine dioxide delignification of hardwood pulps 92

4.4.4 Generation of halogenated organic compounds (AOX, VOX and OX) 96

4.4.5 Bleach plant control in D stages 107

4.4.6 Trouble shooting in D stages 107

4.5 Alkaline extraction 111

4.5.1 Oxidative reinforced extraction 115

4.5.2 Hydrogen peroxide in extraction 121

4.5.3 Decomposition of hydrogen peroxide in bleaching 129

4.5.4 Other alkali sources in extraction 133

4.5.5 Extraction stage control 137

4.5.6 Trouble shooting in extraction 137

4.6 Hydrogen peroxide bleaching 139

4.6.1 Brown stock addition 139

4.6.2 Brightening of unbleached pulp 139

4.6.3 Second extraction stage peroxide application 141

4.6.4 Final bleaching with peroxide, high density storage bleaching 142

4.6.5 Catalyzed peroxide delignification/bleaching 147

4.6.6 Corrosion of titanium by alkaline peroxide 149

4.6.7 Trouble shooting in P stages 150

4.7 Ozone in pulp delignification 152

4.8 Exotic bleaching chemicals 158

4.8.1 Peracetic acid 158

4.8.2 Peroxymonosulfuric acid (Caro's acid) 161

4.8.3 Enzymes 162

4.8.4 Chlorine 164

4.8.5 Hypochlorite 165

4.8.6 Polyoxometalates 166

4.9 TCF bleaching of pulp 169

4.9.1 TCF bleaching of Kraft pulp 169

4.9.2 ECF "light" bleaching of Kraft pulp 171

4.9.3 TCF bleaching of sulfite pulp 172

4.10 Yield in bleaching 181

4.11 Water consumption, effluent "free" processes 189

5 Stability of brightness 201

5.1 Final bleaching with chlorine dioxide or peroxide 210

5.2 Final bleaching with peracetic acid or ozone 218

5.3 Brightness stability in TCF and ECF "light" bleaching 222

6 Bleaching of mechanical pulp 227

6.1 Reductive bleaching 230

6.1.1 Bleaching with bisulfite 230

6.1.2 Bleaching with dithionite 231

6.2 Metals management, use of chelants (sequestering agents) 232

6.3 Bleaching with hydrogen peroxide 234

6.4 Conventional activation and stabilization 235

6.5 Modified peroxide activation 242

6.6 Technology of mechanical pulp bleaching 252

6.7 Control strategy in bleaching 256

6.8 Trouble shooting in mechanical pulp bleaching 256

7 Brightening of secondary fiber 261

7.1 Recycling of paper and board 261

7.2 Recycling for printing paper 265

7.3 Recycling for production of tissue 272

7.4 Recycling for production of board 273

7.5 Trouble shooting in deinking plants 273

8 General aspects of pulp production 277

8.1 Pulp strength 277

8.2 Wood resources 278

8.3 Emissions to the atmosphere 283

8.4 Emissions to the aquatic environment 285

8.5 Solid waste 288

9 Bleaching of other material 291

10 Outlook 297

10.1 Chemical pulp bleaching 297

10.2 Mechanical pulp bleaching 302

10.3 Wastepaper bleaching 303

10.4 Summary 304

Biographical sketch 307

Subject index 309