-
ALKALINE PEROXIDE MECHANICAL
PULPING OF OIL PALM FRONDS VASCULAR
BUNDLE FIBRES
by
OWOLABI FOLAHAN ABDULWAHAB
TAIWO
Thesis submitted in fulfilment of the requirements
for the degree of
Doctor of Philosophy
November 2016
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ACKNOWLEDGEMENT
Prima facea, I am grateful to almighty Allah (SWT) for granting me good health and
well-being that were necessary to complete this study. I am glad for the opportunity to thank
the many people who have encouraged and supported me as I worked toward completion of
this dissertation.
I am grateful to my research supervisors, Dr. Arniza Ghazali, for her pragmatic
supervision and also to my co-supervisors: Prof. Dr.Wan Rosli Wan Daud and Associate Prof.
Abbas Fadhl Mubarek AlKarkhi for their valuable contributions to my Ph.D research study.
I am eternally grateful for the kindness and support of Prof. Dr. Othman Sulaiman and
the wife Prof. Rokiah Ashim both in private and official capacity. My sincere thanks also go
to Associate Prof. Dr. Leh Cheu Peng, Dr. Mazlan Ibrahim, En. Abu Mangsor Mat Sari, (Pak
Abu) for their support and encouragement, while not forgetting the beautiful pieces of advice
and guide given by my mentor Dr. Rushdan Ibrahim. May almighty Allah reward you all
accordingly and abundantly.
My appreciation also goes to Dr. Wan Noor Aidawati Wan Nadhari, Dr. Rohaizu
Roslan, Dr. Khadijah Olateju, Dr. Abdullah Abdurhman Dr. Fahmi Awwalludin and Ustaz
Ajijolakewu for their contributions in this thesis draft.
I owe my brother Surv. (Alh.) Bashir Olayinka Kadiri, Engr. (Alh.) Mohammed
Hassan Bello and Mr. Salawu a debt of gratitude for their unflagging support to my family
throughout my journey away from home. I thank my fellow lab mates for the stimulating
discussions, for the sleepless nights we were working together before deadlines, and for all
the fun we had over the years.
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TABLE OF CONTENT
ACKNOWLEDGEMENT ii
TABLE OF CONTENT iii
LIST OF TABLES xi
LIST OF FIGURES xiii
LIST OF ABBREVIATIONS xvii
LIST OF SYMBOLS xix
ABSTRAK xx
ABSTRACT xxii
CHAPTER 1 INTRODUCTION 1
1.1 General Background 1
1.2 Pulp and Paper Lignocellulose 2
1.3 Problem Statement 4
1.4 Research Objectives 5
1.5 Structure of Dissertation 6
CHAPTER 2 LITERATURE REVIEW 8
2.1 Current Overview of Global Pulp and Paper Industries 8
2.2 Pulp and Paper Production 16
2.3 Pulping Technique 16
2.4 Hybrid Form of Pulping: Chemi-Mechanical Pulping 20
2.5 New Techniques in Pulping 21
2.5.1 Bio-Pulping Technology: 22
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2.5.2 Organosolv Pulping 22
2.6 Alkaline Peroxide Mechanical Pulping (APMP) 23
2.6.1 Pre-Conditioning with Refinesr Chemical APMP (PRC-APMP) 24
2.6.2 Enzymology in APMP 26
2.7 Alkaline Peroxide Pulping (APP) 27
2.7.1 History of Alkaline Peroxide in Industrial Revolution 28
2.7.2 Chemistry of Alkaline Peroxide Pulping 29
2.7.3 System with Alkaline Peroxide Treatment of Lignocelluloses 31
2.7.4 APMP of Various Biomass 36
2.7.5 Alkaline Peroxide Treatment of Oil Palm Biomass 38
2.7.6 Production of Nanolaminates 42
2.8 Biomass 44
2.8.1 Properties of Pulp and Paper Making Fibres 45
2.8.2 Suitability of Non-Wood for Pulp and Paper 48
2.8.3 Types of Non-Wood Fibre 49
2.8.4 Agricultural Residues - Promising Alternative to Wood Fibre 50
2.8.4(a) Special Products from Agricultural Residue 52
2.8.5 Advantages of Using Agricultural Residues 52
2.8.5(a) Economic Viability 52
2.8.5(b) Environmental Challenges 53
2.8.5(c) Technological Simplicity 53
2.9 Plant Based Natural Fibres 54
2.9.1 Processing of Plant Based Natural Fibres 55
2.10 Oil Palm Biomass 57
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2.10.1 Anatomy of OPF 59
2.10.2 Extraction of Oil Palm Biomass for Paper Making 60
2.11 Chemistry of Delignification 60
2.12 Correlation Between Bonding and Strength Properties in Paper 61
2.13 Bonding of Fibres in Paper 63
2.13.1 Inter-fibre Bonding in Paper 63
2.13.2 Van der Waal´s Interaction 64
2.13.3 Hydrogen-Bonding 65
2.14 Fibre Morphological Modification 66
2.15 Experimental Design for APMP of OPF 67
CHAPTER 3 EXPERIMENTAL METHODOLOGY
70
3.1 Introduction 70
3.2 Materials and Methods 72
3.2.1 Raw Material Preparation 72
3.2.2 List of Basic Chemicals Used in the Experiment 75
3.3 Characterisation of OPF Fibres 75
3.3.1 Morphological Analysis 76
3.3.1(a) Fibre Maceration and Measurement 76
3.3.1(b) Derived Values 77
3.3.2 Chemical Composition 77
3.4 Effect of AP on Extracted OPF Fibres 78
3.4.1 Preparation of Cooking Chemicals 78
3.4.2 AP Treatment of the OPF Vascular Bundle 78
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3.4.3 Refining Process 81
3.4.4 Pulp Screening 82
3.4.4(a) Preparation of Pulp Stock 83
3.4.5 Pulp Characterisation 84
3.4.5(a) Kappa Number 84
3.4.5(b) Determination of Residual Klason Lignin 86
3.4.6 Canadian Standard Freeness 86
3.4.7 Characterisation of the Extracted Cellulose 87
3.4.7(a) X-ray Diffraction Analysis 87
3.4.7(b) Fourier Transform Infrared (FT-IR) Spectroscopy 88
3.4.7(c) Thermogravimetric Analysis (TGA) 88
3.4.7(d) Scanning Electron Micrograph (SEM) 89
3.4.8 Fibre Quality Analyser (FQA) 89
3.4.9 Paper Formation 91
3.4.10 Paper Characterisation 92
3.4.10(a) Physical Properties of Handsheet 92
3.4.10(b) Handsheet Thickness 92
3.4.10(c) Grammage 93
3.4.10(d) Apparent Density 94
3.4.10(e) Optical Properties of Handsheet 94
3.4.10(f) Strength Properties of Handsheet. 94
3.4.10(g) Tensile Strength 95
3.4.10(h) Tear Resistance 96
3.4.10(i) Burst Strength 97
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3.4.10(j) Effect of AP Treatment and Reaction Duration 97
3.4.10(k) Scanning Electron Microscope (SEM) 98
3.4.11 Surface Modification of Handsheet 98
3.5 Study of Cooking Variables for APMP of OPF 99
3.5.1 Experimental Design 99
3.6 Regression Model Development 101
CHAPTER 4 DIMENSIONAL CHARACTERISATION OF THE OPF
VASCULAR BUNDLE FIBRES
103
4.1 Characterisation of OPF Vascular Bundle Fibres 103
4.2 Dimensional Analysis 104
4.3 Chemical Composition of OPF Vascular Bundle 109
4.4 Elemental Analysis and Microscopy 113
4.5 Conclusion 115
CHAPTER 5 EVALUATION OF AP PERCENTAGE TREATMENT
LEVEL AND REACTION DURATION ON THE
PROPERTIES OF THE RESULTANT PULP.
116
5.1 Introduction 116
5.2 Evaluation of the Pulp from AP Treatment of the OPF 117
5.2.1 Screened Pulp Yield 117
5.2.2 Kappa Number 121
5.2.3 Canadian Standard Freeness 126
5.3 Fibre Flexibility and Conformability 128
5.3.1 Effect of AP Concentrations on Pulp Fibre Fines Distribution 130
5.3.2 Effect of Cogenerated Fibre Fines 132
5.4 Morphology of Alkaline Peroxide Extracted OPF Fibres 135
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5.4.1 Thermal Characterisation of OPF APMP Pulp 136
5.4.2 X-Ray Diffraction 139
5.4.3 Correlation between FTIR, DTG and XRD 142
5.5 Effect of Alkaline Peroxide Concentration on Paper Apparent Density 147
5.6 Effect of AP Concentrations on the Strength Properties of OPF Paper 151
5.6.1 Strength and Apparent Density Correlation of OPF Vascular Bundle
Paper 158
5.7 Effect of AP Treatment on Inter Fibre Bonding Strength 163
5.8 Effect of AP Treatment on Optical Properties of OPF Paper 165
5.9 Surface Morphological Transformation of Paper from OPF 170
5.10 OPF VB APMP Pulp Network Enhancement 175
5.10.1 Effect of Nanocoating on Paper Printability 176
5.11 Conclusion 177
CHAPTER 6 OPTIMIZATION OF AP VARIABLES 180
6.1 Introduction 180
6.2 Statistical Output 183
6.3 Regression Model Development 187
6.4 Effect of Selected Independent Variables 193
6.4.1 Screened Pulp Yield 193
6.4.2 Kappa Number 197
6.4.3 Tensile Index 199
6.4.4 Burst Index 202
6.4.5 Tear Index. 205
6.4.6 Optical Properties 207
6.5 Elucidating the Correlative Effect of the Response Variables 212
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6.6 Optimization of Alkaline Peroxide Treatment 215
6.6.1 Confirmatory Experiment 217
6.7 Conclusion 219
CHAPTER 7 CONCLUSION AND RECOMMENDATION 221
7.1 Recommendation 223
REFERENCES 225
APPENDIX 267
LIST OF PUBLICATIONS
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LIST OF TABLES
Page
Table 2.1 Annual Paper Production From Malaysian Paper Mills 15
Table 2.2 Common Pulping Method for Lignocellulosic Materials 18
Table 2.3 Active Radicals and Anions from H2O2 Decomposition
in Alkaline Medium
31
Table 2.4 Progress in the Development of AP Treatment System 33
Table 2.5 Physico-Chemical Properties of Some Non-Woods
Used For Papermaking
47
Table 2.6 Categories of Plant Based Natural Fibres 55
Table 3.1 Overview of the General Experimental Work 72
Table 3.2 List of the Chemicals Used in the Study 75
Table 3.3 RSM Experimental Design Summary for AP pulping of
OPF
99
Table 4.1
Data of Dimensional Properties from OPF Vascular
Bundle
104
Table 4.2 Comparison of Morphological Properties of Selected
Lignocellulosic Biomass
106
Table 4.3 Chemical Compositions of OPF VB and Selected
Lignocellulosices Biomass
110
Table 5.1 ANOVA for AP Level and Reaction Duration Effect on
the Properties of OPF VB Fibres Network
118
Table 5.2 Standard Error for the Kappa Number 123
Table 5.3 Crystallinity Index of the OPF Vascular Bundle Fibres 140
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Table 5.4 Assignments of FTIR Absorption Bands of OPF
Vascular Bundle Fibres.
145
Table 5.5 ANOVA for AP Treatment and Time Effect on Pulp
Network Strength Properties
148
Table 5.6 DMRT for AP Treatment on Pulp and Paper Properties. 162
Table 5.7 ANOVA for Effects of AP Concentration and Reaction
Duration on Paper optical properties.
169
Table 5.8 Paper Printability 177
Table 6.1 Experimental Design Matrix Result from Box–Behnken
RSM.
181
Table 6.2 ANOVA of the Pulp and Paper Properties of the OPF
Vascular Bundles Fibres
185
Table 6.3 Correlation among the APMP Variables 213
Table 6.4 Optimal Condition for APMP of OPF VB 216
Table 6.5 Responses at the Optimum Condition of APMP for OPF
VB
217
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LIST OF FIGURES
Page
Figure 1.1 Pulp and paper lignocelluloses biomass. 3
Figure 2.1 Oil palm biomass residues Source: (Dungani et al., 2013). 10
Figure 2.2 Schematic diagram of PRC-APMP process (Source:-Andritz
2004)
25
Figure 2.3 ANDRITZ MSD Impressafinesr for P-RC APMP. 26
Figure 2.4 Oil palm fibrous biomass wastes. 57
Figure 2.5 Schematic diagram of oil palm frond. 58
Figure 2.6: OPF Monochrome photography (Hashim et al., 2011). 59
Figure 2.7 Monomers of lignin. 61
Figure 2.8 Hydrogen bonding at the cellulose fibre surface with water. 65
Figure 3.1 Schematic diagram of OPF vascular bundle fibres. 70
Figure 3.2 Overview of the general experimental work. 72
Figure 3.3 Schematic transformation of leaveless OPF midrib to
vascular bundles.
73
Figure 3.4 Sample of milled OPF vascular bundle fibres particles. 74
Figure 3.5 Sieve shaker machine and sieve plates. 74
Figure 3.6 Motorized laboratory press. 79
Figure 3.7 Schematic diagram for the alkaline peroxide mixing with
OPF.
80
Figure 3.8 Andritz Sprout Bauer single disc refinesr. 81
Figure 3.9 Somerville screener. 82
Figure 3.10 Glassed pulp disintegrator. 83
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Figure 3.11 Canadian Standard Freeness tester. 86
Figure 3.12 Sherwood fibre quality analyzer. 90
Figure 3.13 Semi-automated laboratory Handsheet making machine. 91
Figure 3.14 Micro gauge of Précision Micrometer. 93
Figure 3.15 BrightimeterTM Micro S-5 brightness and opacity tester. 94
Figure 3.16 Frank PTI horizontal tensile testing machine. 95
Figure 3.17 Tear testing equipment. 96
Figure 3.18 Burst testing equipment. 97
Figure 4.1 Fibre dimensions. 105
Figure 4.2 SEM-EDX analysis of the raw OPF biomass. 114
Figure 5.1 Effect of AP concentration on yield with varying OPF VB-
AP reaction duration.
119
Figure 5.2 Reject percentage. 121
Figure 5.3 Effect of AP concentration and time on Kappa number. 123
Figure 5.4 Effect of chemical charge and time on CSF. 127
Figure 5.5 Graph of CSF and bulk estimating conformability of the
fibre.
128
Figure 5.6 Schematic diagram of the various crystallinity conditions of
AP fibres
130
Figure 5.7 Fibre length distribution of OPF pulp produced under optimal
condition.
132
Figure 5.8 Effect of AP concentration and time on cogenerated fines. 133
Figure 5.9 Scanning Electron Micrograph of OPF vascular bundle intact
surface and transformation to fibrillated mass after APMP
system.
135
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Figure 5.10 TGA curves for OPF vascular bundle fibres. 137
Figure 5.11 DTG curve of the raw and extracted OPF VB fibres. 138
Figure 5.12 X-ray diffractometry patterns of APMP pulp from OPF
vascular bundles.
141
Figure 5.13 FTIR spectra of OPF VB fibres. 143
Figure 5.14 Effect of AP treatment on paper apparent density. 149
Figure 5.15. Effect of AP treatment duration on the tensile index of OPF
fibre web.
151
Figure 5.16 Effect of AP treatment duration on the burst index of OPF
fibre web.
153
Figure 5.17 Effect of AP treatment duration on the tear index of OPF fibre
web.
155
Figure 5.18 Correlation between paper apparent density and tensile
index.
159
Figure 5.19 Tensile energy absorption (TEA) at different AP
concentrations.
163
Figure 5.20 Effects of AP concentrations on ISO brightness. 166
Figure 5.21 Effect of AP concentrations and time on paper opacity. 167
Figure 5.22 SEM images of AP paper web at different AP concentrations. 171
Figure 5.23 Effect of EFB nanolaminate coating on OPF APMP paper
strength.
175
Figure 6.1 Normal percentage probability and studentized residual plots
for (A) Screened pulp yield and (B) Kappa number of
alkaline peroxide pulp.
190
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Figure 6.2 Normal percentage probability and studentized residual plots
for (C) tensile index and (D) burst index of alkaline peroxide
pulp and paper properties.
191
Figure 6.3 Normal percentage probability and studentized residual plots
for (E) tear index and (F) ISO brightness of alkaline peroxide
pulp and paper properties.
192
Figure 6.4 Normal percentage probability and studentized residual plots
for (G) Opacity of alkaline peroxide pulp and paper
properties.
193
Figure 6.5 3-D Response surface plot for screen yield.. 195
Figure 6.6 3-D Response surface plot for Kappa number. 198
Figure 6.7 3-D Response surface plot for tensile Index. 200
Figure 6.8 3-D Response surface plot for burst Index. 203
Figure 6.9 3-D Response surface plot for tear Index. 206
Figure 6.10 3-D Response surface plot for ISO brightness. 208
Figure 6.11 3-D Response surface plot of the paper opacity. 209
Figure 6.12 Optimum conditions for APMP of OPF VB. 218
Figure 6.13. Predicted vs experimental outcome at optimality. 219
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LIST OF ABBREVIATIONS
ABS Alcohol Benzene Solubility
A.D. Anno Domini (Before Christ)
ANOVA Analysis of Variance
AP Alkaline Peroxide
API Alkaline Peroxide Impregnation
APMP Alkaline Peroxide Mechanical Pulping
APP Alkaline Peroxide Pulping
BBD Box-Behnken Design
CCD Central Composite Design
CGF Cogenerated Fines Fibres
CMP Chemimechanical Pulping
CMR Chemical-Mechanical Refining
COD Chemical Oxygen Demand
CSF Canadian Standard Freeness Expressed in Terms of Millilitres
CWT Cell Wall Thickness
DF Degree Of Freedom
DPTA Diethylenetriaminepenta Acetic Acid
EC European Commission
EDTA Ethylene Diamine Tetra Acetic Acid
EFB Empty Fruit Bunches
FAO Stat Food and Agricultural Organization Statistics
FL Fibre Length
FT-IR Fourier Transform Infrared
H2O2 Hydrogen peroxide
HWS Hot Water Solubility
ISO International Standards Organization
KBr Potassium bromide
LD Lumen diameter
L/D Lumen Width/Fibre Diameter
LSC Light Scattering Coefficient
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MOA Ministry of Agricultural
MPPMA Malaysian Pulp and Paper Manufacture Association
Mt Metric Ton
NaOH Sodium hydroxide
OPF Oil Palm Frond
OPF VB Oil palm fronds vascular bundles
OPFB Oil Palm Fruit Bunches
OPT Oil Palm Trunk
PSI Pounds Per Square Inch
PTI Paper Testing Instrument
PRC-APMP Pre conditioning with refinesr chemical in Alkaline Peroxide
Mechanical Pulping
R&D Research and Development
RR Runkel Ratio
RSM Response Surface Methodology
SEM Scanning Electron Microscopy
SPSS Statistical Package For Social Sciences
SS 1% Sodium hydroxide Solubility
TAPPI Technical Association of the Pulp And Paper Industry
TCF Totally Chlorine Free
TEA Tensile Energy Absorption
USA United States of America
VB Vascular bundles
WRV Water Retention Value
wt/wt Weight by Weight
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LIST OF SYMBOLS
oC Degree Celsius
Nm Nanometer
Mm Millimeter
µm Micrometer
ml. Millilitre
mN Millinewton
mN/m² Millinewton per square metre
g/m² Gramme per square meter
L Litre
Nm/g Newton meter per gramme
kPam2/g Kilopascal square meter per gramme
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PEMULPAAN MEKANIK PEROKSIDA BERALKALI BAGI BERKAS
VASKULAR PELEPAH KELAPA SAWIT
ABSTRAK
Penyelidikan ini mengkaji kualiti bagi pulpa dan kertas yang diperoleh daripada
rawatan peroksida beralkali (APMP) berkas vaskular pelepah kelapa sawit (OPF) dari
spesis Elaeis guineensis. Matlamat utama kajian ini adalah untuk mengkaji potensi
OPF VB sebagai sumber gentian bagi penghasilan pulpa melalui teknik APMP, yang
dijana melalui proses pemulpaan mekanik peroksida beralkali (APMP). Kesan
penskrinan bagi berkas vaskular OPF dirawat AP dilakukan pada kepekatan AP yang
berbeza. Kepekatan-kepekatan ini termasuk kepekatan AP rendah (1.0%: 1.5%; NaOH:
H2O2), sederhana (2.0%: 2.5%; NaOH: H2O2) and tinggi (4.0%: 5.0%; NaOH: H2O2).
Kesan-kesan bagi pembolehubah heterogen pemulpaan peroksida beralkali (APMP)
(masa pememasakan, kepekatan natrium hidroksida dan kepekatan hidrogen
peroksida) terhadap sifat-sifat pulpa dan kertas (hasil penskrinan, nombor Kappa,
indeks tegangan, indeks koyakan, indeks kepecahan, kecerahan ISO dan kelegapan),
telah dikaji untuk menentukan keadaan operasi yang optimum. Kaedah permukaan
sambutan (RSM) menggunakan rekabentuk Box-Behnken menunjukkan gentian-
gentian berkas vaskular OPF adalah sebandigan degan gentian kayu lembut dan kayu
keras yang digunakan sebagai pulpa komersil dalam pembuatan kertas. Keputusan
setara menunjukkan bahawa biojisim OPF VB yang melalui proses APMP
menghasilkan pulpa terskrin dalam anggaran 45% - 63%. Analisis statistik
menunjukkan aras bererti bagi kesan kepekatan AP terhadap semua sifat-sifat pulpa
dan kertas yang dikaji pada aras keyakinan 95%, degan sokongan imej melalui
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mikroskopi imbasan elektron (SEM). Model-model regresi yang dibentuk
menunjukkan keadaan operasi optimum telah dicapai melalui 2.35% NaOH, 5.00%
H2O2 dan tindakbalas antara OPF VB-AP pada 53.41 minit masa masakan. Keputusan
ini adalah hasil pulpa maksimum yang diskrin (53.39%), dengan keputusan maksimum
bagi sifat-sifat kertas (cth., indeks kepecahan, indeks koyakan, indeks tegangan,
kecerahan ISO dan kelegapan) iaitu 6.55 kPam2/g, 6.22 mNm2/g, 9.92 Nm/g, 28.50%
and 99.71%, masing-masing beserta 80.27 nombor Kappa. Berkas vaskular OPF telah
menunjukkan potensinya sebagai gentian alternatif dan sumber bahan mentah bagi
penjanaan pulpa dan kertas melalui pemulpaan mekanik peroksida beralkali yang
mesra alam lagi ekonomik.
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ALKALINE PEROXIDE MECHANICAL PULPING OF OIL PALM
FRONDS VASCULAR BUNDLE FIBRES
ABSTRACT
This study investigates the quality of pulp and paper obtained from alkaline
peroxide (AP) treatment of oil palm (Elaeis guineensis) fronds (OPF) vascular bundle
or OPF VB. The principal aim of this study is to assess the potential of OPF VB as raw
material and fibre source for pulp production via Alkaline Peroxide Mechanical
Pulping (APMP). Screening effect of AP treated OPF VB fibres was carried out at
different AP concentrations. These concentrations include AP prepared at low (1.0%:
1.5%; NaOH: H2O2), medium (2.0%: 2.5%; NaOH: H2O2) and high (4.0%: 5.0%;
NaOH : H2O2) concentrations. The effects of heterogeneous APMP variables (i.e.,
cooking time, sodium hydroxide concentrations and hydrogen peroxide
concentrations) on the pulp and paper properties (screened pulp yield, Kappa number,
tensile index, tear index, burst index, ISO brightness and opacity), were studied to
determine the optimum operating conditions. Response Surface Methodology (RSM)
using Box-Behnken design was used to explore the effect of selected variables on the
different responses. Results indicated that the vascular bundle fibres compare
favourably with the softwood and hardwood fibres used as commercial pulp for paper
making. The results equally revealed that the biomass was pulpable with AP liquor and
subsequent refining, resulting in screened pulp yield ranging from 45% to 63%.
Statistical analysis shows significant effect of AP concentrations on all of the pulp and
paper properties at 95% confidence level, in line with the morphological changes
acquired from Scanning Electron Microscopy (SEM). Regression models show that the
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optimal operating conditions of the AP were found to be 2.35 % NaOH, 5.00 % H2O2
and a 53.41 minutes cooking time. This results in maximum screened pulp yield
53.39% paper strenght value i.e., burst index, tear index, tensile index, ISO brightness
and opacity were 6.55 kPam2/g, 6.22 mNm2/g, 9.92 Nm/g, 28.50 % and 99.71%,
respectively with 80.27 Kappa number. The OPF VB fibres were shown to be a
potential alternative fibrous raw material for pulp and paper application and this was
made possible via the environmentally compatible and economic APMP process.
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CHAPTER 1
1 INTRODUCTION
1.1 General Background
Pulp and paper demand and consumption are a function of the level of
development and civilization of the humanity. This implies that the more developed
a nation is, the more the rate of pulp and paper consumption. The demand for pulp
and paper fibre resources is largely determined by the society’s dependence on
paper, paper boards and other related products for human welfare. The Directorate
General of Manufacture Based Industry (DGMB), Ministry of Industry Indonesia
reported that global demand for paper has grown by 2.1% annually (Adi et al., 2016).
Pätäri et al., (2016) reported that an increase in the global population would lead to
the enhancement of paper needs. According to the report, the global population and
economic growth predominantly focusing on developing and emerging countries is
expected to increase by 1.3 billion inhabitants by 2030. Hence, industries such as pulp
and paper is expected to brace up to the sustainability of the sector. Presently, despite
an increasing transition to digital media usage, the global pulp and paper industry still
enjoys the benefit from an increased pulp based product consumption (Ajani, 2011;
Lovins & Cohen, 2011). The Paper consumption kg/capita as of 2014 was: North
America (221); EU (56); Japan (215); China (75); Korea, Taiwan, Hong Kong,
Singapore & Malaysia (159); Latin America (47) and Africa (8). On average, each
person consumed 57 kg of paper in 2014 (RISI, 2016). This level of per capita
consumption is due to some factors, which include; the economic growth; increasing
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literacy rate; changing demographics with higher urbanization (Huang 2016). Other
factors include increasing living standards, aspirations for changing lifestyles and
growth of mass communication, which demands for high-quality paper and paper
products (Goryakin et al. 2015).
It is projected that by 2021, the global paper production would rise to 521
million tonnes per annum. Out of this projected figures, 177 million tonnes (44%) is
expected to originate from Asia while the remaining 225 million tonnes (56%) would
come from elsewhere (Perkins & Rawski, 2008).
1.2 Pulp and Paper Lignocellulose
Wood has been the primary paper fibre for less than a century, with paper pulp
demand being predominantly used as writing-printing paper, newsprint and industrial
paper (packaging and wrapping paper, and paper board) (Holik, 2012). Global paper
demand has resulted in two out of every five trees cut for pulp, , which is one of the
main reasons for the destruction of forests worldwide (Middleton, 2013). Wood
sourced pulp and paper has been characterized by a heavy-duty industrial process to
turn wood into paper (Main, et al., 2015). Wood pulping processes release large
amounts of dangerous pollutants, such as chlorine, dioxin and furans into the air and
water bodies (Udohitinah & Oluwadare, 2011). As forests diminish and public opinion
to save forests grows, there is increasing interest in alternative fibre crops (Laftah and
Wan Abdul Rahman, 2016). Fig. 1.1 shows the common sources of lignocellulose used
in pulp and paper industries (Leponiemi, 2008).
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Lignocellulose biomass contain cellulose, hemicellulose, lignin and extractives
with the ratio of these components varying depending on the species of wood. While
some of the fibres are virgin fibres, some are obtained from- recycle papers and non-
wood fibres. The management of the forest biodiversity is a concept towards the
preservation of some characteristic flora and fauna in the tropical region (Kozuka,
2013).
Figure 1.1 Pulp and paper lignocelluloses biomass.
Traditionally wood has been considered as the major raw biomass for paper
making. Countries with limited forest size and limited plantation area like China are
more prone to the used of non-wood as raw material for paper making (Carlsson et al.,
2009; Ai & Tschirner, 2010; Mossello et al., 2010). There is significant growth of
regional imbalances in the fibre supply globally due to shortage supply of virgin pulp.
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The continued rivalry in the fibre demand for pulp and paper, housing and wood for
fuel has equally contributed to the reduce dependency of pulp and paper industries on
virgin pulp (Carlsson et al., 2009; Ai & Tschirner, 2010; Mossello et al., 2010). Sequel
to this development, agricultural residues, such as cereal straws of wheat, rice, barley
and lately empty fruit bunches (introduced by EKO paper mills Malaysia) has been
gaining increasing interest as fibrous source of raw materials in the pulp and paper
industries (MPOB, 2012). In fact, utilisation of the agricultural residue as raw material
for pulp and paper making would ameliorate the persistence waste management
problems.
1.3 Problem Statement
Currently, due to the shortage of wood fibres and economic outlay the use of
non-woods in pulp and paper production in several available and wood deficiency
countries have been gaining increasing attention. Despite the noticeable deficiencies in
the use of non-woods with respect to woods (Fazeli et al., 2016), agro wastes have been
receiving increasing considerations as source of natural cellulose fibre in agro-based
industries including pulp and paper industries. This development is as a result of
imminent environmental instability in the area of biodiversity. Since the introduction
of agro waste as alternative to wood in pulp and paper manufacture, biomass such as
corn stalks (Daud et al., 2016), wheat and rice straws (Reddy and Yang, 2015), have
been used for commercial pulp and paper making. Many research reported on the use
of EFB for pulp and paper (Dermawan et al., 2014; Daud and Law, 2010; Ghazali et
al., 2012), leaving the oil palm (Elaeis guineensis) fronds vascular bundle fibres yet
fully investigated.
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5
A number of methods of fibre extraction have been assessed in the literature
(Daud and Law, 2010; Reddy and Yang, 2015), most of, which operate at high
temperatures and pressures and a few of them releasing environmental hazardous
effluents. Pulping industry has been reported as the second largest polluting industry
after mining (Singh et al., 2014). Air contaminants released from pulping include
particulate matter, sulphur dioxide, and total reduced sulphur (TRS) compounds. To
counteract the pollution issue, adoption of an eco-friendly technique with economic
criteria is needed. To this date, Alkaline Peroxide Mechanical Pulping (APMP) is the
best known technique that not only fit the aforementioned criteria but is also flexible
in its operational size and quality of pulp as the end-product quality. Since the
introduction of alkaline peroxide mechanical pulping by Cort and Bohn in the late 80s,
many Kraft mills in China had been converted to an APMP system (Ghazali, 2006) and
research continue to flourish around the use of various non-wood material, except the
oil palm frond, OPF. This study therefore delves into the Alkaline Peroxide Mechanical
Pulping of OPF VB by accomplishing the following objectives:
1.4 Research Objectives
a) To study the chemical and morphological properties of fibre residing the OPF
vascular bundle.
b) To study the thermal, morphological and chemical changes in the AP- treated
OPF vascular bundle by the use of TGA, SEM and FTIR of the extracted fibres
respectively.
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6
c) To further characterize the effect of the alkaline peroxide treatment on the
strength, optical and morphological properties of the handsheet from the AP-
treated OPF vascular bundle fibres.
d) To develop regression model using RSM via Box Behnken design of experiment
to determine the most improved and enhanced OPF pulp and paper properties.
1.5 Structure of Dissertation
The thesis consists of seven chapters that employ the use of instrumental
analysis, empirical and statistical modelling approach to determine the suitability of
OPF vascular bundle fibres as an alternative source of fibre for pulp and paper products.
Therefore in this dissertation:
Chapter 2: reviews the literature on the use of alkaline peroxide in pulp and
paper making. The suitability of non-wood and agricultural residue for pulp and paper
was enumerated. Furthermore more light on the benefit of the utilization of the
statistical tool in developing and optimizing the pulping condition for pulp and paper
production brought to the fore.
Chapter 3: contains all the experimental approaches undertaken in this study
and gives an insight to the various tools used to analyze the obtained result.
Chapter 4: reports the result of analysis and Characterisation of the OPF
vascular bundle fibres.
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7
Chapter 5: presents the outcome of the preliminary investigation of the alkaline
peroxide treatment duration and level effects on the pulp and paper properties of the
oil palm fronds vascular bundle fibres.
Meanwhile, Chapter 6: presents the result of the combined effects of three
independent variables (hydrogen peroxide concentrations, sodium hydroxide
concentration and cooking time) on the pulp and paper properties of the OPF vascular
bundle fibres using Box Behnken model of the Response Surface Methodology (RSM)
for experimental design. The chapter reports the analysis and process optimization
modelling of the alkaline peroxide treatments on the pulp and paper properties.
The work is wrapped up in Chapter 7 by evaluation of the extent in , which the
objectives had been achieved as well as recommendations for future research to
overcome the identified challenges pertinent to APMP of OPF VB.
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CHAPTER 2
2 LITERATURE REVIEW
2.1 Current Overview of Global Pulp and Paper Industries
Pulp and paper mills are big business around the world, generating $563.6
billion in revenue during 2013 (Singh et al., 2014). The global paper and paperboard
demand as at 2011 stood at 402 million tonnes per annum whereas about 7,745 mills
existing globally can produce only 192 million tonnes of pulp. The paper demand has
almost doubled in 20 years from 242.79 million tonnes in 1990 to 402 million tons by
2011. Paper consumption and production growth in Asia is expected to double by 2030
from 2010 levels (Alexandratos & Haen, 1995; Golley & Tyers, 2006; Oh et al., 2010).
In tropical countries like Malaysia, oil palm plantation has constituted one of
the major source of gross national income (GNI). In Malaysia the oil palm export
constituted $22.31 billion USD to the country’s gross national income in 2014 and it
is expected to rise to $55.8 billion USD by the year 2020 (Awalludin et al. 2015). Food
and Agricultural Policy Research Institute FAPRI (2010) predicts that Malaysian palm
oil production will increase by 26.5 percent, to 23.4 million tonnes by 2020, slightly
less than the predicted Indonesian production of 28.5 million tonnes (Ivancic and Koh,
2016). Oil palm industry in Malaysia with its 6 million hectares of plantation, produced
biomass as much as 100 million tons (Abdul Khalil et al., 2010). In order to maintain
steady growth of oil palm plantation, large areas of primary and secondary forest have
been cut or burned down to make way for oil palm plantations in Indonesia and
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9
Malaysia, the two countries , which produce 80.5% of the world’s palm oil (Ivancic
and Koh, 2016 ).
The conducive climatic condition of Malaysian climate has contributed
absolutely to the growth of oil palm plantation, making it the most important
agricultural crop in Malaysia and has contributed immensely to the national economic
growth (Leibo, 2015). This has made Malaysia the second world largest producer of
oil palm.
The rapid growth of the palm oil industry in South-East Asian countries like
Malaysia is as a result of the palm oil being the world’s largest source of edible oil and
hence constitutes its major economic crop. This has contributed to the expansion of the
area of plantation and making Malaysia the second largest producer of oil palm after
Indonesia (Ivancic and Koh, 2016). The types of waste biomass generated in oil palm
industries in Malaysia as shown Fig 2.1 are generated from both the mill and the
plantation site (Dungani et al., 2013). Fig. 2.1 shows that oil palm fronds, (OPF), and
the oil palm trunks, (OPT), are generated from the plantation sites while the empty fruit
bunches (EFB), palm oil mill effluent (POME), mesocap fibre (MF), and Kernel Shell
(KS) are generated from the oil palm mill.
Increase in oil palm plantation translates to the huge generation of the oil palm
biomass, globally over 190 million tonnes of solid and liquid residues are being
generated from the palm oil industries. In Malaysia, about 100 million tonnes dry
weight of these biomass wastes is projected by 2020, of , which the OPF constitutes
70% and is considered the highest (Wanrosli et al., 2007). These biomass are usually
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10
left on the site resulting to environmental issues while undergoing decomposition,
which is aimed at fertilising the soil (Lim et al., 2000). Oil palm fronds are agricultural
residues by-product biomass generated from oil palm activities and made up of the
petiole, rachis and leaflets.
Figure 2.1 Oil palm biomass residues Source: (Dungani et al., 2013).
Owing to its abundance, biodegradability and problem of disposal, has
contributed to the present currently increases farming costs. In addition it has lead to
environmental deterioration through pollution, fires, and pests. According to Abdul
Khalil and co-workers (2008), oil palm frond contains various sizes of vascular bundle
fibres imbedded in thin-walled parenchymatous ground tissue. While the parenchyma
cells act as a storage medium, the vascular bundle fibres act as mechanical support for
the oil palm frond. This growth of the palm oil industry has caused a corresponding
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11
increasing in the biomass wastes derived from the pruning management practices and
replanting operations (Daud and Law, 2010; Paltseva et al., 2016).
Malaysian and Indonesian based researchers have been saddled with research
and development into economic viability of oil palm wastes in order to minimise if not
totally eradicates the environmental issues associated with the poor management of the
biomass. Biomasses such as agricultural crops and residues, forest resources and
residues, and municipal wastes are the largest source of cellulose in the world
(Awalludin et al. 2015). Among the merits of non-wood plants include short growth
cycles, moderate irrigation and fertilization requirements and low lignin content
resulting to reduced energy and chemicals use while pulping (Wang & Chen, 2013).
Agricultural by-products are annually renewable, available in abundance and of limited
value at present. The use of non-wood fibres and agricultural wastes in papermaking
has been proposed by some environment advocates as a way to preserve natural forests
and prevention of global warming. EFB have proven to be useful raw material for the
pulp and paper industries (Rushdan, 2002).
In countries where the supply of wood resources is inadequate, the rate of paper
consumption continue to be on the increase despite the challenges of commercial
papermaking with respect to limited wood resources. Many ecological problems
occasioned by deforestation such as global warming, hurricanes, flooding, droughts are
among some of the detrimental global environmental problem facing humanity
(Middleton, 2013). While global campaign towards improvement in reforestation has
been on the increase, the utilisation of agricultural residues have attracted the interest
of environmentalist and scientist. The suitability of these agricultural biomass through
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12
various analytical investigation has been the first step in their utilization. For paper
making, the morphology and chemical properties of fibres of the lignocelluloses for
pulp and paper are of great importance to the suitability of pulping and papermaking
processes, as well as for final paper products.
In India, the pulp and paper industry is divided into three sectors based on the
raw materials usage (Reddy & Ray, 2011). These include:-
a) The wood based mills , which comprise of 26 large integrated paper mills using
both wood and bamboo, contributes to 31% production of the mill production
and this translates to 3.19 million tonnes of pulp per annum.
b) The 150 agro-based mills constitute about 25% of the total output and
c) The 538 recycle fibre mills contribute to 4.72 million tonnes, or 47% total
paper product.
In Malaysia, the total capacity of the paper mills is about 50 T/day that
translates to about 1,300,000 T/year. Of all these, integrated pulp and paper mill in
Sipitang, Sabah (Sabah Forest) uses wood fibres (Grafton & Jago, 2013). Table 2.1
shows the total annual production capacity of the paper mills in Malaysia and the actual
production per annum.
It is apparent that the production capacity per annum is short 10.52% of the
total annual capacity of the of the mills. This shortfall is attributable to the lack of raw
material and the maintenance culture of the machinery, , which often breakdown.
There are significant regional differences in pulp and paper consumption and
production patterns. Asia is the biggest region in term of paper consumption and
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production, about twice as big as the North America (Fontagné & Fouré, 2013; Taylor
et al., 2013). Perhaps the most striking fact is that Africa’s paper consumption and
production are so extremely low compared to the other region. The paper making
process thus far has mainly used wood materials from the cut, debarked, chipped, and
pulped tree stems. The continual growth in pulp and paper production entails massive
deforestation.
The pulp and paper industry is currently facing broad structural changes
because of global shifts in demand and supply (Hujala, (2013), as a result of the short
supply of wood materials. This challenge has led to the reductions in the number of
pulp and paper mills, lower rates of capacity growth, employment downturns, and a
loss of market share to foreign competitors (Brown and Wang 2015). These structural
shifts portray an industry that has encountered difficulty in adapting to a more
competitive environment and earning sufficient profits to generate a return on
investment that covers opportunity cost. These changes have significant impacts on
most national economies worldwide. Increasing competition for wood supplies for
construction purposes coupled with gradually rising costs of wood have generated
renewed interest in the use of nonwood plant fibres for papermaking in the highly
industrialized countries (Smith, 1997). It is interesting to note that some environment
advocates have proposed the use of non-wood fibres in papermaking as a way to
preserve natural forests and prevention of global warming.
Both wood and non-wood resources are currently being exploited for the
manufacturing of pulp, paper and paper boards. In countries where the supply of
wood resources is inadequate, the rate of paper consumption has been on the increase
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despite the challenges of commercial papermaking with respect to limited wood
resources.
The use of agricultural residues in pulping and papermaking is gradually
gaining attention because of the problem of disposal, , which currently increases
farming costs and causes environmental deterioration through pollution, fires, and pests
(Bajpai, 2015). In 2003, Malaysia’s Eko Pulp & Paper Sdn Bhd (Company No. 590644-
K).
(EPP) was established in joint collaboration with Forest Research Institute of
Malaysia (FRIM) and Malaysian Palm Oil Board (MPOB) to undertake research and
development and commercialization of pulp production using the oil palm Empty Fruit
Bunches (EFB) (MPOB 2012).
Many ecological problems occasioned by deforestation such as global
warming, hurricanes, flooding, droughts are among some of the detrimental global
environmental problem facing humanity(Middleton, 2013). Many attempts have been
made to simplify the design of the mill to achieve the reduction in the effect of the
economies of scale (Karltorp & Sandén, 2012).
The global pulp production is expected to increase simultaneously with the
consumption of paper, and this is especially through for fines paper with 6.5% increase
in global non-woods consumption (Laftah and Wan Abdul Rahman, 2016). In China
and India over 70% of raw material used by the pulp industries come from non-woody
plants and agricultural residues such as reeds, bamboo, bagasse and cereal straw (Al-
Mefarrej et al., 2013 ). Biomasses such as agricultural crops and residues, forest
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15
resources and residues, and municipal wastes are the largest source of cellulose in the
world. Non-wood plants offer several advantages including short growth cycles,
moderate irrigation and fertilization requirements and low lignin content resulting in a
reduced energy and chemicals consumption during pulping (Wang & Chen, 2013).
Table 2.1 Annual Paper Production from Malaysian paper mills
No. Company Total Capacity per Annum
(mt)
Production per
Annum (mt)
1 Cita Peuchoon 30,000 24,000
2 Johmewah 35,000 8,000
3 Genting Sanyen 300,000 250,000
4 MudaPaper
(Kajang)
170,000 140,000
5 Muda Paper (S.
Prai)
130,000 140,000
6 Malaysia
Newsprint
250,000 250,000
7 Nibong Paper 60,000 60,000
8 Pascorp Paper 140,000 135,000
9 Pembuatan Kertas
(Perak)
3,000 3,000
10 Sabah Forest 165,000 165,000
11 Kimberly-Clark 45,000 35,000
12 See Hua Paper 12,000 10,000
13 Talping Paper 2,400 2,400
14 Then Seng Paper 15,000 11,500
15 Trio Paper 30,000 23,000
16 Union Paper 12,400 6,000
17 United Paper
Board
80,000 60,000
18 Yeong Chaur S 3,600 3,600
TOTAL 1,483,400 1,327,300
(Source:- MPPMA- 2003)
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Agricultural by-products are annually renewable, available in abundance and
of limited value at present.
2.2 Pulp and Paper Production
Modern pulp and paper manufacturing evolved from the ancient art first
developed in China, ca. 105 A.D (Singh et al., 2014). Papers are manufactured from
cellulosic fibres, generally wood (composed cellulose, lignin, hemicellulose, and
extractives (e.g., resins, fats, pectins, etc.)), recycled paper, nonwood raw materials
such as bagasse, cereal straw, bamboo, reeds, esparto grass, jute, flax, and sisal and
agricultural residues (Main et al., 2015). In principle, papers are made by raw material
preparation (wood chipping and size reduction) and handling, Pulp manufacturing (to
separate and clean the fibres), Pulp Washing and Screening, Chemical recovery,
Bleaching, Stock Preparation, and Papermaking (Samariha and Khakifirooz 2011). The
main goal of pulping process is to remove as much lignin as possible without sacrificing
fibre strength, thereby separating the fibres and removing impurities that can cause
discoloration and paper instability. Hemicellulose, which is similar to cellulose in
structural composition and function plays an important role in fibre-to-fibre bonding in
papermaking. Other components of wood that are removed during pulping process are
extractives (e.g., oleoresins and waxes).
2.3 Pulping Technique
Two basic processing steps are involved in pulp and paper production this
include the conversion of fibrous raw material into pulp followed by the conversion of
the pulp into paper. This processes could be achieved mechanically or chemically. The
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pulp is then bleached and further dispersed in water and reformed into a web,
depending on the type and grade of paper that is needed to be produced (Bajpai 2015).
Table 2.2 gives the common pulping method for lignocelluloses materials. The first
step in pulping is the cost efficient and environmental sound pulping technique even at
small scale. This is what forms the interest of researchers exploring the avenue of using
non-wood and agricultural residue as alternative raw material to wood. Globally,
several factors have contributed to increasing the level of industry interest in the use of
nonwood and agricultural residue as fibre sources. Some of these factors include :-
(a) environmental pressure to stop using trees due to deforestation
(b) projections of world fibre shortage by 2010 (Jepma, 2014), and the need to
find alternative fibre sources
(c) abundance of agricultural residues (such as corn stover, sugar cane bagasse,
banana pseudostem and wheat straw) that are otherwise burned off fields
and
(d) opportunities of integrated mill to produce multiple products (oils, textile
fibres, papermaking fibres, board fibres, plastics, food) from a simple fibre
source, , which provides unique opportunities for sustainable agriculture.
Among the qualities governing good pulp and paper material in paper
production is, increasing the amount of cellulose and decreasing the value of lignin, the
extractive content, and the percentage ash content. All these result in increased yield,
a decrease of chemical material consumption, and cooking time (Panshin & Zeeuw,
1980).
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Table 2.2 Common Pulping Method for Lignocellulosic Materials
Pulping
method
Chemical used Properties of isolated pulp Application of pulp Refences
1 Kraft/
sulphate
Sodium hydroxide +
sodium sulphide
Strong, low brightness
(dark brown)
Making boxes, paper bags and
wrapping paper. Can also be used
for writing paper and paperboard
when bleached.
(Kim et al., 2016)
2 Sulphite Sulphurous acid / sodium
sulphite
High flexibility and
requires little bleaching
Used in making paper and special
purposes.
(Moradbak et al.,
2015)
3 Soda Sodium hydroxide +
anthraquinone
Have properties similar to
sulphite
Ideal for all paper uses. (Wutisatwongkul et
al., 2016)
4 organosolv Organic solvents and
organic acids
Properties still under
review
Preliminary results suggest
multi-purpose uses.
(Moral et al., 2016)
5 Biopulping Involve the use of white
fungus
Increase tear index, low
Kappa number and other
properties are still under
investigations.
Results suggest possible uses in
all aspects of the paper.
(Singhal et al., 2015)
6 APMP/PRC-
APMP
Hydrogen Peroxide+
Sodium hydroxide
High yielding pulp, high
iso-brightness, right paper
properties
Ideal for all paper uses (Cort and Bohn, 1991)
7 APP Hydrogen peroxide +
Sodium Hydroxide
Same as obtained for
APMP
Preliminary laboratory result
suggest multi-purpose use
(Ghazali et al., 2009)
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The second step is the choice of pulping technique. Among the array of the
environmentally friendly pulping is alkaline pulping, organosolv pulping, and Chemi-
mechanical pulping (Sridach, 2010; Bajpai, 2013a).
There are three principal groups of pulping processes namely mechanical
pulping, chemical pulping and bio-pulping. Mechanical pulpingis a pulping method
that uses disc refinesr on raw wood (mainly softwood) against the abrasive surface with
the aim to de-fibre the raw material without the dissolution of lignin (Harinath et al.,
2013). Khakifirooz et al., (2012b) reported that this method is characterized by high
yield and usually more than 95% of the dryweight of the wood. High temperature and
pressure are used by some methods to increase the efficiency of the process. Although
mechanical pulping generates very low polluting effects but is an energy intensive
process, as the non-cellulosic wood components are not available conversely to what
obtain in chemical pulping (He et al., 2013). Chemical pulping involves the dissolution
of all the non-cellulosic components of the lignocelluloses biomass in cooking liquor
at high temperature and pressure thereby separating the fibres. Generally chemical
pulping gives better paper quality (Biermann, 1996; Bajpai, 2013a). However it is
characterized with greater environmental pollution (through its pulping and bleaching
process), capital intensive and operating costs are higher than those of mechanical
pulping. The yield of chemical pulping is about 50% of the dryweight of raw material.
An example of the method is: sulphate or kraft, sulphite, and soda pulping.
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2.4 Hybrid Form of Pulping: Chemi-Mechanical Pulping
Hybrid pulping is another form of pulping, which involves a chemical pre-
treatment of the raw material, before a mechanical treatment to liberate the fibres. The
yields of these processes are situated between those for mechanical and chemical
pulping (Hosseinpour et al., 2014).
Chemi-Mechanical Pulping (CMP) has gained global attention as an
environmental benign pulping method (Khakifirooz et al., 2012b). It is a type of hybrid
pulping process involving impregnation of raw material with small amounts of
chemicals to soften the lignin, while it then employs mechanically treatment to liberate
the fibres. Masrol and co-workers (2015) reported that the pulp yields of these
processes are situated between those for mechanical and chemical pulping, due to the
synergistic operations of the two pulping protocol in CMP. Cort and Bohn (1991)
observed that heat is typically applied to improve pulping. The report further revealed
that this method is characterized by good fibre properties, low chemical application,
lower capital and operating costs compare to pure mechanical pulping. Chemi-
mechanical pulps can be used for low- to medium-quality papers, and with additional
processing they may be used for some high-end purposes. However,the most popular
and widely accepted process is the invention of a new CMP technology called
alkaline peroxide mechanical pulping (APMP) (Cort and Bohn, 1991). However, the
dissolved lignin and the other trace elements in the biomass are treated and discharged
into the environment.