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Full Text in DIVA Aspects of optimizing pulp fibre properties for tissue and packaging materials Hafizur Rahman Main supervisor: Prof. Armando Cordova Co-supervisors: Prof. Per Engstrand Asst. Prof. Börje Norlin Faculty of Science, Technology and Media Thesis for Doctoral degree in Chemical Engineering Mid Sweden University Sundsvall, 2021-06-14 Akademisk avhandling som med tillstånd av Mittuniversitetet i Sundsvall framläggs till offentlig granskning för avläggande av teknologie doktorsexamen i kemiteknik, Måndagen den 14:e juni, 2021 klockan 10:00 i sal C312 , Mittuniversitetet Sundsvall. Seminariet kommer att hållas på engelska. Aspects of optimizing pulp fibre properties for tissue and packaging materials © Hafizur Rahman, 2021-06-14 Printed by Mid Sweden University, Sundsvall, Sweden ISSN: 1652-893X ISBN: 978-91-89341-15-9 Faculty of Science, Technology and Media Mid Sweden University, SE-851 70 Sundsvall, Sweden Phone: +46 (0)10 142 80 00 Mid Sweden University Doctoral Thesis 348 iii iv Table of contents ABSTRACT ....................................................................................................... viii SAMMANFATTNING .......................................................................................... ix LIST OF PAPERS ................................................................................................ x CONTRIBUTION TO THE PAPERS .................................................................... xi LIST OF RELATED PAPERS AND PUBLICATIONS ........................................ xii CONFERENCES AND SEMINARS ................................................................... xiii ABBREVIATIONS AND ACRONYMS ............................................................... xv DEFINITIONS .................................................................................................... xvi INTRODUCTION .................................................................................................. 1 Scope ....................................................................................................... 1 1.2 Objectives of the study ........................................................................... 3 BACKGROUND ................................................................................................... 5 2.1 The composition of wood ....................................................................... 5 2.2 Production of kraft pulp.......................................................................... 6 2.3 The carbohydrate yield in kraft pulping ................................................ 7 2.4 Modification of kraft pulp by selective cooking ................................... 9 2.5 Characterization of the fibre properties .............................................. 10 2.5.1 Fibre strength ................................................................................. 10 2.5.2 Tensile strength ............................................................................. 10 2.5.3 Fibre/fibre joint strength ................................................................. 10 2.5.4 Surface charge .............................................................................. 10 2.5.5 Fibre swelling ................................................................................. 11 2.6 Effect of refining .................................................................................... 11 2.7 Suction box dewatering ........................................................................ 11 2.8 Uniformity of impregnation at the fibre level ...................................... 12 2.8.1 Scientific studies on degree of sulphonation ................................. 13 2.8.2 New miniaturized XRF technique for sulphonation study .............. 14 2.9 Catalytic approach to improve selectivity .......................................... 15 v 2.9.1 Lignin is a natural source of vanillin ............................................... 16 2.9.2 Reaction of lignin during oxygen delignification ............................. 17 EXPERIMENTAL ............................................................................................... 19 3.1 Materials ...................................................................................................... 19 3.1.1 Sulphate cooking (I) (II) ................................................................. 19 3.1.2 Vanillin synthesis (V) ..................................................................... 19 3.2 Methods.................................................................................................. 19 3.2.1 Preparation of pulps (I-III) .............................................................. 19 3.2.2 Sheet preparation (I) (II) ................................................................ 21 3.2.3 Physical testing (I) (II) .................................................................... 22 3.2.4 Charge analysis (I) ......................................................................... 22 3.2.5 Analytical procedure for vanillin synthesis (IV) .............................. 23 3.3 Instruments ............................................................................................ 24 3.3.1 Gas chromatography (GC) (I) ........................................................ 24 3.3.2 Differential scanning calorimetry (DSC) (I) ( II) .............................. 24 3.3.3 PulpEye analysis (II) ...................................................................... 26 3.3.4 Britt dynamic drainage jar (BDDJ) (II) ............................................ 26 3.3.5 Dewatering (laboratory scale) (II) .................................................. 27 3.3.6 Instrument setup for ED-XRF (III) (V) ............................................ 28 3.3.7 Instrument setup for vanillin synthesis (IV) .................................... 30 RESULTS AND DISCUSSION ........................................................................... 32 4.1 Impregnation improvement by selective cooking .............................. 32 4.1.1 The difference in yield of kraft pulps (I) (II) .................................... 32 4.1.2 Effect of yield on physical properties (I) ......................................... 34 4.1.3 Hemicellulose yield and dewatering properties (II) ........................ 37 4.1.4 Hemicellulose yield and fibre characteristics (I) (II) (V) ................. 40 4.2 The uniformity of impregnation at fibre level ..................................... 45 4.2.1 Simulation model to validate the ED-XRF setup (III) ..................... 46 4.2.2 Validation of helium gas in XRF setup (III) .................................... 47 4.2.3 Measurement of Na and S from pulp sample at XRF (III) (V) ........ 49 vi 4.3 Improving selectivity with a catalytic cooking system (IV) ............... 51 4.3.1 Effect of oxygen consumption on vanillin yield .............................. 52 4.3.2 Effect of alkalinity on vanillin yield.................................................. 53 4.3.3 Effect of temperature and autoclave time on vanillin yield ............. 54 CONCLUDING REMARKS ................................................................................ 57 5.1 Improved impregnation with selective cooking ................................. 57 5.2 Improved impregnation uniformity with XRF ..................................... 58 5.3 Improved selectivity with a catalytic approach .................................. 58 5.4 Suggestions for further work ............................................................... 59 5.4.1 Further development of kraft pulp modification for tissue .............. 59 5.4.2 Further development of the XRF technique for sulphonation ........ 59 5.4.3 Further improvements in selectivity with a catalytic process ......... 60 ACKNOWLEDGEMENTS .................................................................................. 61 REFERENCES ................................................................................................... 63 vii ABSTRACT To improve the competitive advantages of pulp fibre-based materials for tissue and packaging over fossil-based products, it is essential to increase knowledge of the selectivity of the cooking and the chemimechanical processes by optimizing the unit operations of impregnation, cooking and refining. A general goal in pulping processes is to achieve as efficient and even fibre separation as possible. A key to achieving this is to improve impregnation uniformity. In the case of chemical pulping, we need to study how a more even distribution of lignin at the fibre level via easily impregnated wood chips can be achieved using classic measures such as equalized hydroxide ion concentration, increased initial sulphide ion concentration, low sodium ion concentration and a low cooking temperature combined with an oxidative and reductive environment. In the case of chemithermomechanical pulp (CTMP) manufacturing, we need to achieve as even a degree of sulphonation as possible at the level of the individual fibres by means of improved sulphite ion distribution within the wood chips before they are pre- heated prior to entering the refiner. Firstly, we have studied selective cooking systems for sulphate pulp manufacturing in oxidative (polysulfide) and reductive (sodium borohydride) environments. The yield increased from 48% to a maximum of 53%, which resulted in faster dewatering when mimicking a tissue papermaking process. This could explain how the advantage of the increased yield (fewer fibres and a more open sheet structure) outweighs the negative effects
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