Optimization of Sodium Carbonate-Sodium Hydroxide Pulping of Wheat Straw for Corrugating Medium Production
Western Michigan University ScholarWorks at WMU
Master's Theses Graduate College
4-1992
Optimization of Sodium Carbonate-Sodium Hydroxide Pulping of Wheat Straw for Corrugating Medium Production
Irmak Yayin
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Recommended Citation Yayin, Irmak, "Optimization of Sodium Carbonate-Sodium Hydroxide Pulping of Wheat Straw for Corrugating Medium Production" (1992). Master's Theses. 954. https://scholarworks.wmich.edu/masters_theses/954
This Masters Thesis-Open Access is brought to you for free and open access by the Graduate College at ScholarWorks at WMU. It has been accepted for inclusion in Master's Theses by an authorized administrator of ScholarWorks at WMU. For more information, please contact [email protected]. OPTIMIZATION OF SODIUM CARBONATE-SODIUM HYDROXIDE PULPING OF WHEAT STRAW FOR CORRUGATING MEDIUM PRODUCTION
by
Irmak Yayin
A Thesis Submitted to the Faculty of The Graduate College in partial fulfillment of the requirements for the Degree of Master of Science Department of Paper and Printing Science and Engineering
Western Michigan University Kalamazoo, Michigan April 1992
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. OPTIMIZATION OF SODIUM CARBONATE-SODIUM HYDROXIDE PULPING OF WHEAT STRAW FOR CORRUGATING MEDIUM PRODUCTION
Irmak Yayin, M.S.
Western Michigan University, 1992
This study's primary objective was to present sodium
carbonate pulping as an alternative to soda or lime pulping
of wheat straw for corrugating medium production. If
sodium carbonate pulping is comparable with soda pulping in
terms of strength properties, it could be the preference of
choice because the recovery of sodium carbonate is simpler
requiring less capital investment. The two strength
properties that were optimized with respect to total
chemical charge, cooking time, and sodium hydroxide
fraction in the cooking liquor were Concora crush resis
tance and STFI compressive strength. These are the two
most important strength properties for the end use of
corrugating medium. Response surface methodology was used
in conjunction with a central composite experimental design
throughout the study. The data indicate that sodium carbon
ate pulping gives as good a result as soda pulping in terms
of the strength properties investigated. The second part
of the project correlated the strength development to
pentosan and lignin contents of the pulps. This correla
tion depended on the optimization constraints.
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. To the memory of Huseyin Avni Ayata, my grandfather,
whose values and principles will always be the guiding
light of my life .. .
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. ACKNOWLEDGEMENTS
I wish to express my sincere thanks to Dr. Raja
Aravamuthan, my advisor and committee chairperson, for his
valuable guidance throughout the study and for pushing me
to my limits. Without his valuable guidance, this study
would not have been completed. I also wish to thank Dr.
Ellsworth Shriver, my committee member, for his continuous
support, encouragement and advice. A special note of
thanks goes to Dr. Nick Triantafi11opoulos for agreeing to
join my committee, his punctuality and his practical ap
proach. I also thank Dr. Raymond L. Janes for helping me
at various stages.
I wish to express my gratitude to Mr. Richard Reames
who did everything he could to provide the necessary
laboratory equipment. I also would like to thank Mr.
Michael Lapacz, laboratory manager in Green Bay Packaging
Corporation, Green Bay Wisconsin, for his permission to use
their laboratory facilities.
I would like to express my feelings of admiration for
the late Dr. Sarkanen for his modesty and friendly ap
proach. It was a pleasure and an honor for me to meet him.
I also would like to express my feeling of pride and
gratitude in being awarded one of the first graduate
ii
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Acknowledgements— Continued
fellowships by the office of the Vice President for
Research at Western Michigan University.
Last, but not least, my deepest gratitude, thanks and
appreciation are extended to my parents for their moral and
financial support to bring this study to completion.
Irmak Yayin
iii
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Optimization of sodium carbonate-sodium hydroxide pulping of wheat straw for corrugating medium production
Yayin, Irmak, M.S.
Western Michigan University, 1992
Copyright ©1992 by Yayin, Irmak. All rights reserved.
UMI 300 N. ZeebRd. Ann Arbor, MI 48106
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Copyright by Irmak Yayin 1992
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. TABLE OP CONTENTS
ACKNOWLEDGEMENTS...... ii
LIST OF TABLES...... vii
LIST OF FIGURES...... ix
CHAPTER
I. INTRODUCTION...... 1
II. LITERATURE REVIEW...... 5
Physical and Chemical Characteristics of Straw...... 5
Straw Pulping Processes...... 8
Straw Pulping Chemicals...... 11
Sodium Carbonate Pulping...... 17
Inorganic Chemistry of Sodium Carbonate Pulping...... 18
Organic Chemistry of Alkaline Pulping...... 22
Cooking Variables and Their Effect on Pulp Quality...... 23
Effect of Chemical Composition on Strength Development...... 24
Concora Medium Test (CMT) and Edgewise Compressive Strength(ECS): Their Relation to Chemical Structure of Pulp and Physical Properties of Sheet...... 29
III. ANALYSIS OF THE LITERATURE...... 34
Straw Pulping...... 34
Pulping and Development of Strength...... 35
IV. PROBLEM STATEMENT...... 38
iv
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CHAPTER
V. EXPERIMENTAL DESIGN AND SCHEMATIC...... 40
Experimental Design...... 40
Schematic...... 42
VI. METHODOLOGY...... 45
Raw Materials...... 46
Cooking and Washing...... 47
Refining...... 47
Sheet Formation...... 48
Determination of Strength Properties...... 49
Chemical Compositions of Raw Materials and Straw Pulps...... 50
VII. ANALYSIS OF DATA...... 52
Response Surface Methodology...... 54
Application of Response Surface Methodol ogy...... 56
VIII. RESULTS AND DISCUSSION...... 76
Maximization of Strength Properties...... 77
Pulp Yield and Its Correlation With Strength Properties...... 94
The Relationship Between Concora and STFI....101
Chemical Composition of Pulps...... 103
The Relationship Between Chemical Composition of Pulp and the Strength Properties...... 114
The Relationship Between the Optimum Cooking Variables and Optimum Pentosan and Lignin Content...... 143
v
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CHAPTER
IX. CONCLUSIONS...... 161
X. SUGGESTIONS FOR FURTHER STUDY...... 163
LITERATURE CITED...... 165
APPENDICES...... 172
A. Raw Data...... 173
B. Regression Equations and Summary of Statistical Analyses for Data Sets That Correlate Chemical Compositions of Pulps to the Cooking Variables...... 200
C. ANOVA Tables and Regression Equations for Concora-STFI Linear Regression...... 206
D. Sample Calculations...... 210
E. General Information on Straw...... 212
BIBLIOGRAPHY...... 223
vi
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. LIST OF TABLES
1. Cooking Conditions in Phase I Cooks...... 43
2. Cooking Conditions in Phase II Cooks...... 44
3. Tests, Standards and Instruments...... 51
4. Analysis of Variance Table (Concora, First Order Regression, NaOH Cooks)...... 58
5. The SAS Statistical Analysis for Concora Data Set of Pure Sodium Hydroxide Cooks (At the Density of 550 kg/m3 or At 90 Second Refining)...... 60
6 . Analysis of Variance Table (Concora, First Order Regression, Na2C03-Na0H Cooks)...... 68
7. The SAS Statistical Analysis for Concora Data Set of Sodium Carbonate-Sodium Hydroxide Cooks (At the Density of 550 kg/m3 or At 90 Second Refining)...... 70
8 . Concora Spreadsheet for Cook No. 28...... 79
9. Summary of the Statistical Analysis for Concora Data Sets of Pure Sodium Hydroxide Cooks...... 83
10. Summary of the Statistical Analysis for Concora Data Sets of Sodium Carbonate- Sodium Hydroxide Cooks...... 85
11. Summary of the Statistical Analysis for STFI Data Sets of Pure Sodium Hydroxide Cooks...... 89
12. Summary of the Statistical Analysis for STFI Data Sets of Sodium Carbonate- Sodium Hydroxide Cooks...... 92
13. Change in Chemical Compositions With Cooking Conditions (Pure Sodium Hydroxide Cooks)...... 103
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14. Change in Chemical Compositions With Cooking Conditions (Sodium Carbonate-Sodium Hydroxide Cooks)...... 104
15. Nomenclature for the Data Sets That Correlate the Cooking Variables to the Chemical Composition of Pulp...... 105
16. Data Sets for Analyzing the Effects of Lignin and Pentosan Percentages on Strength Properties...... 115
17. Strength Values of Pulps Subject to Different Constraints...... 116
18. Results of Regression of Pentosan and Lignin Contents of Pulp on Strength Properties of Handsheets (Sodium Hydroxide Cooks)...... 117
19. Results of Regression of Pentosan and Lignin Contents of Pulp on Strength Properties of Handsheets (Sodium Carbonate- Sodium Hydroxide Cooks)...... 118
viii
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. LIST OP FIGURES
1. Wheat Straw 6
2. Structural Components of Wheat Straw (3, p. 84)....6
3. Bast Cells of Fibers From the Internodes of Wheat Straw (x 30) (3, p. 84)...... 7
4. Equilibrium Constant of Sodium Carbonate Decomposition At Different Temperatures (34, p. 797)...... 21
5. First Order Orthogonal Experimental Design...... 40
6 . Composite Second Order Experimental Design...... 41
7. First Order Region for NaOH Cooks...... 57
8 . Second Order Region for NaOH Cooks...... 58
9. Verification of Maximum Found by SAS Analysis Concora vs. Chemical Charge at 17.58 Minutes...... 59
10. Three Dimensional Representation of the Second Order Concora Model for NaOH Cooks...... 64
11. Three Dimensional Representation of the Second Order Concora Model for.NaOH Cooks (Axes are Rotated 903)...... 65
12. Contour Plot of the Second Order Concora Model for NaOH Cooks...... 66
13. First Order Region for NajCOj-NaOH Cooks...... 67
14. Second Order Region for Na2C03-Na0H Cooks...... 69
15. Three Dimensional Representation of the Second Order Concora Model for NajCOj-NaOH Cooks...74
16. Contour Plot of the Second Order Concora Model for Na2C03-Na0H Cooks...... 75
17. Concora Regression Line for Cook No. 28...... 80
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18. The Change of Density and Concora With Refining Time...... 81
19. The Change of Concora and Density With CSF...... 82
20. Three Dimensional Representation of the Second Order Yield Model for NaOH Cooks...... 95
21. Three Dimensional Representation of the Second Order Yield Model for Na2C03-Na0H Cooks.... 96
22. Concora vs. Yield, NaOH Cooks...... 99
23. Concora vs. Yield, NajCOj-NaOH Cooks...... 99
24. STFI vs. Yield, NaOH Cooks...... 130
25. STFI vs. Yield, Na2C03-Na0H Cooks...... 100
26. The Relationship Between Concora and STFI (NaOH Cooks)...... 101
27. The Relationship Between Concora and STFI (Na2C03-Na0H Cooks)...... 102
28. Contour Graph of Kappal Data Set...... 106
29. Contour Graph of Ligretl Data Set...... 108
30. Contour Graph of Penretl Data Set...... 109
31. Contour Graph of Kappa2 Data Set...... Ill
32. Contour Graph of Ligret2 Data Set...... 112
33. Contour Graph of Penret2 Data Set...... 113
34. Contour Graph of CSOD1 Data Set...... 120
35. Contour Graph of RCONSOD11 Data Set...... 121
36. Contour Graph of RCONSOD22 Data Set...... 122
37. Contour Graph of CSOD2 Data Set...... 123
38. Contour Graph of RCONSOD33 Data Set...... 125
39. Contour Graph of CSOD3 Data Set...... 126
x
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40. Contour Graph of RCONCAR11 Data Set...... 127
41. Contour Graph of RCONCAR22 Data Set...... 128
42. Contour Graph of RCONCAR33 Data Set...... 129
43. Contour Graph of CCARl Data Set...... 130
44. Contour Graph of RSTFISOD11 Data Set...... 132
45. Contour Graph of SSOD1 Data Set...... 133
46. Contour Graph of RSTFISOD33 Data Set...... 134
47. Contour Graph of SSOD3 Data Set...... 135
48. Contour Graph of RSTFISOD22 Data Set...... 137
49. Contour Graph of SSOD2 Data Set...... 138
50. Contour Graph of RSTFICAR11 Data Set...... 139
51. Contour Graph of SCARl Data Set...... 140
52. Contour Graph of RSTFICAR33 Data Set...... 141
53. Contour Graph SCAR3 Data Set...... 142
54. Contour Graph of RSTFICAR22 Data Set...... 144
55. Contour Graph of SCAR2 Data Set...... 145
56. Contour Graph of T4 Data Set...... 147
57. Contour Graph of T1 Data Set...... 149
58. Contour Graph of T2 Data Set...... 150
59. Contour Graph of TALI Data Set...... 152
60. Contour Graph of TAL2 Data Set...... 153
61. Contour Graph of TAL6 Data Set...... 156
62. Contour Graph of TS4 Data Set...... 157
63. Contour Graph of TS1 Data Set...... 158
64. Contour Graph of TASL6 Data Set...... 159
xi
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65. Contour Graph of TASL1 Data Set...... 160
xii
i
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. CHAPTER I
INTRODUCTION
Straw is one of the first raw materials commercially
used in the production of pulp and paper. After the
invention of the fourdrinier paper machine in 1805 and the
cylinder machine in 1809, paper production speeded up and
raw material demand increased. In 1827, commercial pulping
of straw started in a mill in Pennsylvania (1). Several
other mills followed in succeeding years. The relative
ease with which straw could be pulped with inexpensive lime
in an open kettle contributed to its early adoption as a
raw material for many grades of paper and paperboard.
Among these was newsprint which was produced mixing straw
pulp with rag pulp (1). Even though experiments on wood
pulping were successful, resulting in the creation of the
soda, groundwood, sulfite and kraft processes between the
years 1840-1885, straw pulp production expanded and reached
a peak of 2/3 million tpy in 1940. This was mostly due to
the acceptance of straw paperboard for shipping containers
as a substitute for wooden boxes in 1895 (1). In the
meantime, research on semi-chemical pulping of wood was
intensified and the first commercial NSSC process emerged
in 1925 for the manufacture of corrugating board (2).
1
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. After the 1940 record high production, straw corrugating
board production in the U.S. mills declined. This was not
because of lack of quality, but because of the economics of
straw supply (1). In early 1970, the last of the U.S. mills
using straw pulp switched to hardwoods and waste paper (1 ).
Other developed countries in Western Europe experienced
similar trends.
Straw lost its popularity in papermaking in developed
countries having enough wood supply because of its techno-
economical disadvantages compared to wood. These can be
listed as follows:
1. Difficulties in collecting, handling, baling and
storing straw. Straw is a seasonal agricultural product.
Annual requirements of the mills have to be collected
during the short harvesting season (30-45 days) and have to
be stored on the mill site or nearby farm lands. The
collection, baling and storage of straw are labor inten
sive. Storage of the bales is critical because of the
vulnerable nature of straw to moisture. Higher than 8-12%
moisture renders the straw susceptible to rot in storage
and also causes spontaneous combustion resulting from the
intensive heat developed in the stacks due to fermentative
reactions (3). Rotted straw consumes more chemicals during
pulping and gives lower yields and strength (3).
2. Drainage problems of straw pulp. The slow drainage
of straw pulp limits the paper machine speed and requires
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. more capital investment for stock washers (Table 54,
Appendix E).
3. Some inconveniences for the recovery. The three
basic features of straw black liquors which are different
from wood pulp black liquors are their low calorific
values, their highly viscous nature and their high silica
content. All these factors render the recovery operation
difficult.
These factors have eliminated straw pulp production in
many developed countries. However, in many developing
countries that do not have adequate wood supplies, straw
and other non-wood materials still constitute the major
fiber source for pulp and paper industries (1). China by
far is the leader in straw pulp production. According to
a 1986 Pood and Agriculture Organization of the United
Nations (PAO) capacity survey, China produces about 84% of
world's total straw pulp with 5,515,000 tpy production (4).
Other developing countries like Algeria, Argentina, Egypt,
India, Indonesia, Mexico, Pakistan, Sri Lanka, Syria and
Turkey and some European countries like Bulgaria, Denmark,
Greece, Holland, Hungary, Italy, Rumania, Spain and
Yugoslavia produce the other 16% of the world's straw pulp
(3).
According to Atchison (4) and Shouzu (5), the world
wide capacity growth of non-wood plant fiber production has
increased since 1970, going from 6.7% of total world
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. papermaking pulp capacity in 1970 to 8.1% in 1985. It was
projected that this percentage would increase by 1990. The
average annual increase in non-wood plant fiber capacity
(4.7%) is now more than double the average annual increase
in wood-pulp capacity (2%). The greatest part of this
increase is attributed to developing market economies,
especially in Asia (3).
Thanks to its stiff fibers, straw is extensively used
in corrugating medium production. Straw paperboard has
high crushing resistance and compressive strength. High
yield straw pulp for corrugating medium is mostly produced
by lime or lime-soda process. Although soda pulping yields
stronger pulps, the process does not possess the techno-
economical feasibility for corrugating medium production
because the chemical is expensive and most of the straw
pulp mills do not have a recovery operation.
On the other hand, sodium carbonate pulping of
hardwoods has been used in many U.S. high-yield pulp mills
for corrugating medium production since 1972. The recovery
of sodium carbonate is easier than sodium hydroxide since
it does not require a causticizing operation. Hence,
investment dollars needed for the recovery are less. This
study intends to apply sodium carbonate high-yield pulping
to straw. If successful, chemical recovery might be
feasible for medium-sized pulp mills that could afford
causticizer free chemical recovery lines.
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. CHAPTER II
LITERATURE REVIEW
Physical and Chemical Characteristics of Straw
The morphology of straw is quite different than that
of wood (Fig. 1 and 2):
The stems or culms of the cereal straw are erect, elastic and generally tubular. These are separated at intervals by nodes, which occur as vascular bundles crowded together and interlaced to form a strong diaphragm between the internodes. The rachis, or top portion of the stem to which the seed is attached , is generally found with the straw. The leaf, starting at the node forms a sheath part way up the stem and ends in a leaf blade. Chaff consists of small broken pieces of stem, leaf sheath and blade along with various materials, such as seed hulls (glumes) and bristles (awns), which together with the seed and rachis form the head of the plant (3, p. 83).
Straw mainly consists of bast cells, parenchyma, epidermal
cells and vessels. Bast cells exist predominantly in the
internodes and they are the principal source of fiber for
pulping (3). According to Rydholm (6), wheat straw
contains 50% bast and sclyerenchyma fibers, 30% parenchyma,
15% epidermal cells and 5% vessels. Zhai, Zhongzeng and
Diesheng (7) report that the bast cell fibers of wheat
straw have relatively more lignin content and less hemicel-
lulose but have almost the same holocellulose content as
the parenchyma cells. Hence the bast cell fibers contain
5
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 6
RACHIS '!/ \ \
/ NODE ‘ INTERNODE Jv ! LEAF BLADE N LEAF SHEATH ------5 i L
Figure 1. Wheat Straw.
■v ' r ? ' U -I - I -
Figure 2 Structural Components of Wheat Straw (3, p.84)
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. a higher amount of cellulose than the parenchyma cells
(Pig. 3).
Figure 3. Bast Cells of Fibers From the Internodes of Wheat Straw (x 30) (3, p. 84).
Straw contains less cellulose compared to wood but the
holocellulose content is almost the same. Higher pentosan
and lower lignin contents than wood species are the
chemical composition characteristics of straws.
Straw species, among themselves, show considerable
heterogeneity. Their chemical content changes not only
from one species to another but also from one region to
another. Therefore it is only possible to talk about
average values for chemical compositions and the physical
characteristics (Tables 54, 55, 57, 58 and 59, Appendix E).
Average length of wheat straw is reported as 1.5 mm. (1,3)
and its average diameter is reported as 13 to 15 microme-
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. ter (3). According to Misra (3), the excellent paper
formation characteristics of straw fibers are attributable
to their relatively high ratio of average length to
diameter. Wheat and rye are the preferred straws because
papers made of their pulps are stiffer and stronger (3).
Another feature of straws that is different from that
of wood is the high ash content. Silica constitutes the
major part of the ash (Table 57, Appendix E). Rice straw
has the highest silica content among straws (9-14%). Wheat
straw contains less but still a considerable amount of
silica (3-7%). Wood species, on the other hand, contain
less than 1%.
Straw Pulping Processes
Prepulping treatment is a necessity for straw since it
contains appreciable amounts of soil, sand, other impuri
ties and grains. There are two types of treatment methods
in general: dry and wet. Dry preparation is the most
common method because of its simplicity and its relatively
lower energy consumption. Disc or rotary drum type cutters
are used to reduce the length of the straw to 4 in. in the
U.S. (2.5-3 in. in European mills) (8 , 9). The cut straw
is conveyed pneumatically to screens and cyclones to
separate grain, sand and dust present along with the straw.
The wet preparation system essentially is based on the use
of a hydropulper fitted with an extraction plate and a
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. rotor that are specially designed so that the sand, grit
and leafy materials are separated and eventually escape out
of the pulper through a valve (8). The wet cleaning system
is suggested especially for rice straw which contains
comparatively high amount of silica even though power,
repair and maintenance costs of wet process are higher
(10). The new Naco process uses a modified wet pretreat
ment. Straw bales are broken up and treated with hot water
and sodium hydroxide (50°C, 1-2% conc.) at 5% consistency
in a hydropulper (11). It is reported that the silica
content is reduced by about 40% with this method (8).
A batch or a continuous system can be used for pulping
of straw. Continuous pulping system permits rapid cooking
of straw and other non-wood fibers with less energy,
chemicals and man hours. It also permits lower liquor-to-
straw ratios; hence the spent liquor has a higher solids
content and needs less steam for evaporation to the
required concentration level (3). Batch digesters, on the
other hand, are preferred because of their greater flexi
bility. Straw pulping conditions have to be often changed
depending on the moisture content, cleanliness and morpho
logical characteristics of the straw based on soil condi
tions and other factors (12). In addition, batch digesters
are easier to feed. Some problems encountered in this
respect with continuous digesters are reported in the
literature (13).
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 10
Some of the well known patented cooking systems
applied for straw pulping are reported as follows: (a)
Celdecor-Pomilio, (b) Pandia and Defibrator, (c) Celdecor-
Kamyr, (d) Escher-Wyss MCP, (e) Saica, (f) HP (Hojbygaard
Papir Pabrikkar), (g) Mechano-Chemical, and (h) Naco.
Except for the Mechano-chemical and the Naco process
es, the other six processes look alike. Celdecor-Pomilio
is the oldest continuous pulping process, having been
developed in the 1930s. Pulping and bleaching are inte
grated in this system. However, it is always possible to
produce unbleached semi-chemical pulp by discarding the
chlorination part of the process. A vertical digester is
used as in the Celdecor-Kamyr system. Pandia, Escher-Wyss,
Saica and HP systems use horizontal or inclined digester
tubes. Celdecor-Pomilio, Pandia and Kamyr are pressurized
systems whereas HF, Saica and Escher-Wyss are working under
atmospheric pressure. Chemicals used depend on the paper
grade to be manufactured. For corrugating medium produc
tion, all the systems use CaO, NaOH or a combination of the
two. For pressurized systems residence time can be as low
as 8 minutes in the digester while it is longer in non
pressurized systems (8). The mechano-chemical process uses
a hydropulper to treat straw in the presence of pulping
chemicals. It is possible to make bleachable grade pulp by
using a high concentration of NaOH. Pulp for corrugating
medium can be produced by using lime or a lime-caustic
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. mixture.
The Naco process is based on an Italian patent and it
uses caustic soda and oxygen in a specially designed high-
pressure pulper named turbopulper. This process is being
used to produce bleached pulp. It consists of three major
sections: NaOH pretreatment, turbopulper (delignification)
and oxygen tower (homogenizer). Ozone bleaching following
the oxygen tower is in the pilot plant stage. A Lurgi
recovery plant is constructed for recovery which is similar
to alkaline pulping recovery with the exception that there
is no recausticizing equipment. Recovered Na2C03 is fed
back to the turbopulper and used as a cooking chemical.
Green liquor from the recovery boiler is pretreated with
lime in order to control the level of silica (14).
Straw Pulping Chemicals
A variety of pulping chemicals can be applied to straw
pulping:
1. Lime based
- CaO
- CaO + NaOH
- CaO + Na2C03
2. Soda based
- NaOH
- N*aOH + Clj (Celdecor-Pomilio continuous process,
bleached)
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- NaOH + Anthraquinone
- NaOH + 02
- NaOH + 02 + Anthraquinone
- Cold soda
- NaOH + Na2C03 + 02 (Naco process)
3. Kraft
- NaOH + Na2S
4. Neutral Sulfite
~ N a 2SOj + N a 2COj
- Na2S03 + NaOH
5. Modified Neutral Sulfite
- Na2SOj + Na2S + NaOH .+ (Anthraquinone)
- Na2S03 + Na2S + Na2C03 + (Anthraquinone)
6 . Ammonium based
- Ammonium Sulfite (NH^)2S03
- Ammonium Hydroxide (NH4)OH
7. Potassium based
- k 2s o3 + k 2c o3
8 . Organosolv
- catalyzed (aqueous ethanol in the presence of acids
or salts as catalysts)
- uncatalyzed (aqueous ethanol)
9. Alkaline hydrogen peroxide
- NaOH + H202
10. Green Liquor
- Na2C03 + Na2S
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 13
11. Sodium Carbonate
— NajCOj
Table 60, in Appendix E, lists some non-wood plant
fibers, their end-uses and recommended pulping processes.
Tables 61 and 62, in Appendix E, illustrate the cooking
conditions for the most common pulping methods for some
non-wood raw materials. Lime based pulping results in
coarse pulps of 70-85% yield (3) that are used for corru
gating medium production. However, such lime based semi
chemical pulp from straw suffers in quality. Pulp becomes
difficult to refine and lime builds up on various parts of
paper machine. It has been reported that its production
was stopped in a Hungarian pulp mill because of its failure
to meet quality requirements (15).
Soda and soda-Aq are the most accepted methods for
straw pulping because strength properties of pulps produced
by the soda and sulfate processes show only marginal
differences for most non-wood fibrous materials (10,16).
Neutral sulfite pulps, on the other hand, are freer in
drainage characteristics but their strength properties are
low as compared to pulps produced by soda and sulfate
processes (10). Acid sulfite pulping is not suitable for
non-wood plant fibers. Strength loss and low yield
compared to alkaline processes are reported (3,10).
Soda and sulfate processes are in the predominant
position in China comprising 55% of the total pulp produc-
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tion (5). Neutral sulfite pulp production is declining due
to the lack of recovery and increasing environmental
concerns (5). Green liquor pulping of rice straw for
corrugating medium is reported to be successful (17) but it
has the same environmental drawbacks as neutral sulfite
process.
A neutral ammonium sulfite pulping process for wheat
straw was developed in China. In the late 1960s, the Taian
Paper Mill in China started the first commercial operation
of this kind in the world (18). The spent liquor from the
process is not recovered but is used as a supplementary
source of nitrogen fertilizer in nearby farmlands
(5,18,19). An ammonium hydroxide pulping process was
proposed by Thil laimuthu (20) in 1984 but no further
reports on laboratory or commercial evaluation of this
approach have been reported afterwards (19). It has been
reported that New Fiber International Ltd. of Vancouver,
Canada has recently concluded plans to develop a joint
venture pulp mill in Fujian Province, China. The pulping
process is believed to involve the use of ethanolamine in
a mixture with an alkali such as ammonium hydroxide. The
spent pulping liquor is presumed to be disposed of as an
agricultural fertilizer (21). As stated by Wong et al.
(19), Yamada* had previously studied the use of KOH in the
*Yamada, K. (1978). "Method for Pulping Non-woody Plants", Japan Pat. Kokai 81, 704/78, Japan Pat. Kokai 86, 807/78 and Japan Pat. Kokai 86, 808/78.
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 15
pulping and oxygen bleaching of non-woody plant materials.
It appeared, however, that there is little or no economic
benefit in using KOH instead of NaOH. A co-work of Arbokem
Inc., Canada and Oregon State University on potassium based
sulphite pulping of wheat straw reports comparable results
with sodium based neutral sulfite pulping for the produc
tion of bleachable-grade straw pulp (19). It claims that
the potassium and sulfur chemicals in the spent liquor
become a highly valued fertilizer for the cultivation of
many crops. * The cold soda process is said to be used in order to
manufacture glassine or grease proof papers (10).
A modified neutral sulfite process is proposed in
order to decrease the degradation of carbohydrates and
increase the delignification rate and bleachability by the
addition of small amounts of sodium sulfide (22). Similar
chemicals with higher sodium sulfide concentrations and
with the addition of anthraquinone were suggested for
dissolving pulp production from wheat straw (23). Use of
hydrogen peroxide for dissolving pulp production from wheat
straw is also reported in the literature (24).
Organosolv delignification was originally studied by
Kleinert and Tayenthal (25) as a novel method for producing
chemical pulps for paper manufacture. Chum, Johnson and
Black (26) report the advantages of organosolv delignifica-
tion compared to conventional kraft pulping processes as a
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substantial reduction in capital costs and higher pulp
yields for the same level of delignification. The two
broad categories of organosolv processes are catalyzed and
uncatalyzed. The catalysts can be acids or salts.
Organosolv recovery is simpler than conventional pulping
processes (16). Production of bleachable hardwood pulps by
the alcohol pulping and recovery process by extraction has
been confirmed on the pilot plant scale (27). Laboratory
scale studies on organosolv pulping of wheat straw for
bleachable grade chemical pulps with quite acceptable
strength properties were reported (27, 16). However, there
is not any commercial application yet.
Soda-oxygen and soda-aq-oxygen pulping of non-wood
fibers are reported by different authors (28, 29, 30).
Production of high quality chemical pulps from straw
in a short cooking time by carbonate under oxygen pressure
was proven by Lachenal, Wang and Sarkanen in 1977 (16).
Another process which uses unusual amounts of carbon
ate is the Naco process. A project of Franco Nardi--an
Italian engineer--on the soda oxygen delignification of
wheat straw was taken up by the Swedish supplier, Sunds
Defibrator, in the early stages of research (14). The
chemicals used in the digestion are NaOH and NajC^ under
high oxygen pressure. This process is currently practiced
on a commercial scale 100 tpd. Italian government pulp and
paper mill which produces printing and writing grades as
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well as stamps and security papers (14,15).
Sodium Carbonate Pulping
Lachenal et al. (16) studied the carbonate cooking of
wheat straw and found comparable strength properties with
Kraft process at the same yield (45%). However, they
suggested a two stage cooking process or a countercurrent
continuous digesting process because carbonate lost its
delignification efficiency in the presence of dissolved
lignin. They reported limited amount of delignification
(70% yield) with one stage-carbonate pulping process. They
claimed that it was due to the competing condensation
reactions that took place when the lignin concentration was
high (16).
Sodium carbonate cooking of hardwoods with the
presence of caustic as an additive has been practiced in
U.S. high-yield semi-chemical pulp mills for the production
of corrugating medium since 1972 (31, 32). The pulp mills
in the U.S. use continuous digesters with the following
process conditions: (a) pressures--145 to 180 psi, (b) %
chemicals on OD wood--4 to 15% (as NajO), (c) NaOH % in the
chemical--! to 25%, and (d) digester residence times--4
min. to 40 min.
Hanson (31) reports three slightly different applica
tions of carbonate cooking used by different mills in the
U.S. :
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1. Owens-Illinois process. The active pulping agent
is a mixture of sodium carbonate and sodium hydroxide. The
ratio of sodium hydroxide to sodium carbonate is very
critical. The patent covers the 15%-50% caustic range as
sodium oxide.
2. Soda ash process. Sodium carbonate (soda ash) is
the active agent and 6% to 8% is used on wood.
3. Modified soda ash process. This process uses a
small amount of caustic soda make-up along with soda ash.
Mills using this process avoid O-I patent claims by adding
only 7%-8% caustic as sodium oxide.
Inorganic Chemistry of Sodium Carbonate Pulping
Sodium carbonate is an inorganic reagent which
dissociates to Na' and COj” ions in an aqueous solution. The
following reactions take place:
Na2C02{a(j) * * 2Na*+C(%~ (1)
C0^~+H20 -r* C02+20H~ (2)
C(%~+C02+H20 I * 2HCO3 (3)
C0^'+H20 * * HCO^+OH- (4)
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h 2o +co2" + h 2co3 (5)
(6)
H2C03 H++HCC% (7)
HCO; H++CO 3 (8)
In an aqueous solution of carbon dioxide, the predomi
nant species is hydrated COj but for convenience is often
considered to be carbonic acid (HjCOj) (33).
As shown by the above chemical equations, sodium
carbonate in water forms a weak aeid-base system. Dis
solved carbon species are carbon dioxide, carbonic acid,
hydrogen carbonate and carbonate ion; water species are
hydrogen ion and hydroxyl ion. When a strong acid is added
to the system, sodium carbonate acts as a buffer and keeps
the pH of the solution in the buffer range. That is why it
is used in NSSC pulping to keep the pulping pH neutral;
thus it allows pulping to proceed under milder conditions.
This results in higher pentosan content pulps than pulps
prepared by any other common process (10).
Carbonate is always present in kraft white liquors
because of incomplete causticizing during recovery. It has
been observed in pulping experiments that sodium carbonate
contributes to the alkalinity at the end of the kraft cook
(34).
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During alkaline pulping, sodium carbonate contributes
to the activity of the cooking liquor at high temperatures
and low alkalinity levels. The equilibrium constant for
sodium carbonate (Kj,) increases with increasing temperature
and the equilibrium of equation 4 shifts toward the right
at low OH' concentrations. The following equations can be
used to compute the hydroxyl ion concentration in the
liquor.
Kb = [HC03'][0H'] / [C03"J (9)
K„ = [Hf][OH'] (10)
Kg = [H+][C03"] / [HCOf] (11)
Kb = Kj, / Kg (12)
Gustafsson and Teder (34) studied the change in
equilibrium constants at elevated temperatures. By using
Fig. 4 and Eq. 9, it is possible to calculate the hydroxyl
ion concentration [OH‘] for a given temperature. The shape
of the curve shows that the hydroxyl ion concentration
increases with increasing temperature. Also higher sodium
ion concentration shifts the equilibrium constant curve and
thus increases hydroxyl ion concentration (Fig. 4).
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»eg Jf,
4 Extrapolated to 0 ionic strength
172 5C
Figure Equilibrium Constant of Sodium Carbonate Decompo- sition At Different Temperatures (34, p. 797).
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 22
Organic Chemistry of Alkaline Pulping
In alkaline pulping, alkali is consumed (a) in reac
tions with lignin; (b) in dissolution of carbohydrates; (c)
in neutralizing various organic acids, both those present
in the original wood and those produced during pulping; (d)
by the resins of the wood; and (e) to some extent by
adsorption on the fibers (35). Of the charged alkali only
25-30% goes to degradation products of lignin during a
kraft pulping operation (36).
The main reactions of lignin auring alkaline pulping
are base catalyzed fragmentation and competing condensation
reactions of lignin (35,36,37). The alkaline delignifi-
cation becomes effective by a combination of two mecha
nisms: Molecular weight degradation and phenolic hydroxy
group formation; and, the acidity of the latter, with
alkali, causes generation of phenoxides and imparts
solubility (37). Ether bonds are less stable than carbon
bonds and easier to break. The most effective increase in
phenolic hydroxy group concentration is achieved by this
way with the cleavage of 3-0-4 linkages. It is reported
that only about 40% of the 3-0-4 linkages were cleaved with
soda pulping while almost 100% cleavage was obtained under
same conditions with kraft pulping (38). The reason is
said to be a greater nucleophilicity obtained by the
addition of SH’ ions.
A variety of condensation reactions is proposed for
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alkaline pulping (35, 36, 37). Condensation occurs by the
reformation of carbon-carbon linkages and causes repoly
merization of fragmented lignin. Condensation diminishes
the solubility of residual lignin and causes reactivity to
decrease (35).
In NSSC pulping, on the other hand, molecular weight
degrading effect of alkaline pulping is combined with the
attachment of hydrophilic functional groups (SOj") to the
molecular fragments. According to Chiang, Funaoka and Wang
(39), wheat straw lignin contains a substantial amount of
p-hydroxyphenyl nuclei in addition to guaiacyl and syringl
nuclei. These three types of phenyl nuclei provide
possible sites for condensation reactions and ease conden
sation reactions. This is in accordance with the findings
of Lachenal et al. (16). They found that the sodium
carbonate cooking of wheat straw is impeded by condensation
reactions.
Cooking Variables and Their Effect on Pulp Quality
It is possible to list the primary cooking variables
in alkaline pulping as follows: (a) temperature and
pressure, (b) time, (c) effective alkali, (d) alkali
concentration, and (e) 1 iquor-to-straw ratio.
Higher temperature, alkali concentration and resi
dence time in the digester increase the delignification
extent. However, the process also becomes less selective
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towards lignin.
According to experimental results of Bray and Curran
(40), in the case of soda process with Lobolly pine using
30% of NaOH on the wood weight, increasing the concentra
tion from 30 to 60 g/L and from 60 to 90 g/L results in an
approximate doubling of the reaction rate for each step
(40). A similar effect by the increase of temperature is
also shown by Bray (41) for soda cooking of spruce.
More recent studies depict the importance of the
cooking variables on the carbohydrate loss. Kondo and
Sarkanen (42) show higher carbohydrate loss with higher
initial temperatures. Teder and Olm (43) emphasize the
importance of alkaline concentration throughout the cook
for selective delignification and they suggest a modified
kraft process as a means of keeping the alkaline concentra
tion lower than for conventional pulping. Genco, Busaya-
sakul, Medhora and Robbins (44) state the importance of
hemicellulose retention and try to maximize the hemicellu-
lose content of the kraft pulp by changing the cooking
conditions.
Effect of Chemical Composition on Strength Development
It is a well known fact that both physical and
chemical structure of fibers have influence on.the final
paper properties. They both are species dependent. The
former further being affected by refining while the latter
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depends on the type, intensity and duration of the pulping
process.
Pulping conditions determine the degree of lignin
removal and carbohydrate dissolution. The final chemical
composition and degree of polymerization of a pulp deter
mine the ability of swelling, conformability, ease of
refining and potential bonding capability of the fibers.
A high degree of polymerization and a high percentage of
hemicellulose content develop higher sheet strength
properties. In contrast, the presence of lignin prevents
swelling of fibers, decreases interfiber bonding and leads
to lower strength properties.
The strength of paper depends on the strength of
fibers, relative bonded area, strength of bonds and the
homogeneity of structure. Bonding is the primary factor in
determining sheet strength. As Ebeling stated (45), it is
generally agreed that the strength of most common papers is
not limited by the weakness of fibers because the specific
strength of cellulosic fibers is orders of magnitude higher
than that of paper. Instead, the strength of paper is
limited by the weakness of the fiber-to-fiber bonds and by
the heterogeneity of the structure of paper. Even though
fiber bonding has a strong effect on the final strength
properties of paper and paperboard, this is not independent
of the intrinsic fiber properties. In other words,
properties of cellulosic fibers affect the fiber-to-fiber
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bonds. These properties can be classified as (45):
1. Physical: Fiber length, fiber diameter, thickness
of the cell wall, degree of swelling before bond formation,
state of external fibrillation, amount and nature of cell
wall irregularities including dislocations.
2. Chemical: Chemical constitution of fiber, topo-
chemical distribution of the various main chemical compo
nents of the cell wall through the cell wall layers, amount
and nature of cellulose crystallinity in the cell wall and
degree of polymerization of the chemical components of cell
wal 1.
Fiber-to-fiber bonding in a paper can be characterized
by specific bond strength and bonded area. Increased
bonded area and higher bond strength give higher strength
properties to papers. The ability of the fibers to form
hydrogen bonds is important for the strength of fiber-to-
fiber bonding. External and internal fibrillation of
fibers and a sufficiently high degree of polymerization for
the fibrillated cell wall determine the hydrogen bond
forming ability of fibers (45).
Increased sheet and individual fiber strength proper
ties with higher hemicellulose retention during pulping
were reported by many authors. Ross (46), in 1950,
analyzed the previous studies on hemicellulose retention
and the relation between the hemicellulose content of pulp
and sheet strength properties. He also performed a series
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of experiments and concluded that the pulp with higher
pentosan content could be beaten more easily and could give
better strength properties.
Cottral (47), in 1950, emphasized Jayme and
Lochmuller-Kerler's early work2. These authors, working
with beechwood, found an optimum hemicellulose content
where strength properties reach a maximum and then begin to
fall. They had proposed two explanations for that:
increasing proportions of short chain hemicelluloses in the
pulp progressively decrease the intrinsic strength of the
bonds, and increasing amounts of hemicelluloses in the
fibers reduce the intrinsic strength of fibers. Even
though these arguments contradict the results obtained by
McIntosh, Leopold and Spiegelberg (48, 49, 50), they never
theless put a question mark on the issue whether it is
enough to determine the quantity of hemicelluloses present
in the pulp or whether their types and degree of polymer
ization are also important. Accordingly, Cottral (47)
pointed out that the fibrous material with a higher degree
of polymerization at the same hemicellulose content should
give stronger paper. However, he also drew attention to
Jayme's statement that there is an upper limit on the
degree of polymerization of about 1100-1400, above which
the increase in strength is little and below which the
2 Jayme, G. , & Lochmul1er-Kerler, E. (November, 1942). Holtz Als Roh u Werkstoff 5, no. 11:377-381.
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 28
decrease of strength becomes more noticeable.
The type of hemicelluloses affects strength. In 1961,
Leopold and McIntosh (48), working with lobolly pine
holocellulose pulps, found that the reduction in individual
fiber strength correlates with the removal of xylan-based
hemicellulose from the fibers. In another study, in 1963,
McIntosh (49) found that mannan content of the fiber is
responsible for the strength of individual fibers in
softwood Kraft pulps. Even though this was contradictory
with his previous study, he concluded that the hemicellu
lose content of fibers is important to internal strength
since it promoted the swelling of the cell wall. In 1966,
Spiegelberg (50) observed a decrease in fiber elastic
modulus of longleaf pine hoiocellulose pulps with decreas
ing hemicellulose content.
Recently, Genco et al. (44) studied the hemicellulose
retention during Kraft pulping. Although they did not make
any strength measurements, they mentioned the importance of
hemicellulose retention during pulping for development of
the final strength properties of paper by referencing older
studies. In one such earlier study, researchers, working
with hoiocellulose pulps, have found an optimum hemicel-
lulose content for strength development as Jayme did.
According to Rydholm (6), the role of hemicelluloses
is partly to improve swelling of the secondary wall which
makes the fibers more flexible and an increase of the area
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for interfiber contact, and to participate directly in the
interfiber bonding. The two mechanisms stated by Genco et
al. (44) are similar to Rydholm's reasoning. The reasons
are: (a) improved bond strength as a result of hemicellu
lose content on the surface of microfibrils, and (b) more
water associated with the fibers resulting in improved
fiber swelling and consequently higher relative bonded
area.
Hemicelluloses are amorphous chemical components as
contrasted to the crystalline alpha-cellulose fibrils.
Consequently, their swelling tendency in water is higher
and their response to refining is faster. The presence of
hemicelluloses in the pulp helps the formation of hydrogen
bonds and increases the bonded area due to their higher
swelling capability.
Concora Medium Test (CMT) and Edgewise Compressive Strength (ECS): Their Relation to Chemical Structure of Pulp and Physical Properties of Sheet
Containerboard performance is often measured by the
box compression test value (BCT) and by the plane compres
sion strength on flat crush test (FCT) . The BCT is a
direct measure of the stacking strength of corrugated board
packages, since the load-bearing properties of a box are
often of decisive importance under modern transport
regulations (51).
According to McKee, Gander andWachuta's (52) empiri-
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cal equation, the compression strength BCT of a corrugated
boxboard is expressed as:
BCT-kxECT0'75 x^/Sb^SE^ '^xZ0-5 (13)
where, Sb is the bending stiffness of the board in Nm, ECT
is the edgewise compressive strength of the board in kN/m,
Z is the periphery of the box in m, and k is a conversion
factor to give BCT in N.
The relationship between ECT of the board and the
compressive strength (ECS) of its components is:
ECT<* (ECSL1+ECSLa+(tECSp) (14)
where, a is the corrugating take up factor (or the ratio of
the length of fluting to the liner), subscript Li corre
sponds to top liner, the subscript L2 corresponds to bottom
liner, and subscript F refers to fluting.
McKee et al.'s equation shows that the maximum load-
bearing ability of the corrugated board box depends not
only on the compression load-bearing ability of the
corrugated board but also on the ability of the box panels,
i.e., its bending stiffness. The bending stiffness for a
given flute height and corrugated board grammage can only
be increased by distributing as much of the board grammage
as possible to the liners and by using a liner with higher
tensile stiffness in the facings of the corrugated board
(51). This explanation suggests that the bending stiffness
of corrugated boards is more sensitive to changes in liner
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properties rather than the corrugating medium specifi
cations .
FCT is a measure of the ability of the corrugated
board to resist compressive forces perpendicular to the
board surface when total crushing of the fluted layer takes
place. This property of containerboard is important
because during converting--die cutting, printing, etc.--the
corrugated board is subjected to high plane compression
forces. The finished corrugated board is also exposed to
loads which exert plane compression forces which the
corrugated board must endure (51).
In light of the above discussion, ECS and CMT are the
two important strength properties for corrugating medium.
According to Bernard and Bouchayer (53), CMT is a
function of the modulus of elasticity, E, the square of
thickness, e, and grammage, G, as expressed by:
CMT°* (ExezxG) (15)
According to Gartaganis and Ostrowski (54), the
elastic modulus of paper should increase with decreasing
yield because of lignin dissolution and consequent increase
in bonding. In their experimental study, with NSSC pulp
prepared from a mixed hardwood furnish, they obtained a
dramatic increase in CMT value in the yield range of 90% to
81.4%. Between 81.4% and 65%, they found only a small
increase. During their experiments, hemicellulose content
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on pulp remained constant at around 15%. In their article,
they drew attention to the contradicting results obtained
by other researchers who tried to correlate CMT value to
total yield: Dahm (55) reported that the maximum obtain
able CMT values were independent from yield when comparing
neutral sulfite and cold soda semichemical pulps for
corrugating medium in the yield range of 84.4% and 78.5%.
Jayme and Schwartzkopf f3 found very small variations in CMT
values in the yield range of 92%-81% with NSSC poplar pulps
(54). Therefore, it can be concluded that there exists a
critical yield value, depending on furnish and cooking
method, above which the Concora value drops sharply. This
critical value probably corresponds to the point where the
minimum amount of lignin dissolution required for Concora
strength development is reached.
Fellers (56) reviewed all previous studies on edgewise
compression strength. He states two complementary failure
mechanisms. One is activated by the buckling of fiber
segments, predominant in low density sheets; the other by
shear dislocations of fiber walls caused by flow of
microfibrils predominant in high density well bonded
sheets. Hence, he concludes that compressive strength is
limited by the fiber modulus in well bonded sheets whereas
it is limited by the bonds in low density sheets. Fellers,
3 Jayme, G. , & Schwartzkopff, V. (1963). Das Papier 17 (12):697 .
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Ruvo, Elfstrom, and Htun (57) show that compressive
strength remains relatively constant over a yield range
from 47% to 66% at a constant density level and hemicellu-
lose content. They suggest that lignin contributes to the
load carrying ability in compression because strength did
not increase with decreasing lignin content and, hence,
with increased bonding.
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. CHAPTER III
ANALYSIS OF THE LITERATURE
Straw Pulping
During the past years, many steps have been taken to
improve the economics of straw pulping. Those include
improvement of continuous pulping methods, more efficient
silica removal methods (10, 58, 59, 60) and use of special
plastic disc for stock refining (61). However, the
requirement for low capital investment for the recovery
remained as the key to the economic operation of straw pulp
mills, worldwide. Most of the straw pulp mills are small
or medium sized. The economies of scale do not allow them
to make the capital investment necessary to build the
conventional kraft recovery systems. By the same reason
ing, high-yield sodium carbonate pulping of straw, if
proven to be compatible in terms of pulp strength proper
ties, can replace the existing pulping processes in medium
sized high-yield straw pulp mills that can afford the
causticizer-free recovery plant investments.
Although studies on the sodium carbonate cooking and
sodium carbonate-oxygen cooking of wheat straw for bleach-
able grades are present in the literature (16, 28, 29, 62),
34
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 35
no study has been found on the sodium carbonate or sodium
carbonate-caustic cooking of wheat straw for corrugating
medium production.
Sodium carbonate cooking of straw was not investigated
as thoroughly as the sodium carbonate cooking of hardwoods
in the U.S., because most of the straw pulp mills were
located in developing countries where environmental
concerns were secondary compared to industrial production.
Furthermore, a few existing European straw pulp mills were
generally integrated with wood pulp mills where cross
recovery was possible.
In straw pulping, the attainment of high strength
values with the soda process proves the fact that straw is
easier to pulp than wood. Kraft and NSSC pulping processes
do not bring any advantages in terms of pulp strength
properties. There is no need for SOj" or SH’ ions. Most of
the ether linkages can be cleaved and solubilized by the
presence of hydroxyl ions. Therefore, there seems to be no
reason to obtain unsatisfactory pulping results with straw
by using a comparatively less active cooking chemical, such
as sodium carbonate.
Pulping and Development of Strength
An appreciable amount of theoretical and experimental
study on the hemicel lulose and lignin retention and on
their effects on sheet strength properties are present in
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the related literature. Even though some of them are
contradictory among themselves, the general belief is that
the strength properties are related to the hemicellulose
and lignin contents of pulps. According to experimental
works and theoretical approaches, hemicelluloses have a
positive effect on the pulp strength properties. However,
cellulose and hemicelluloses are sensitive to most of the
delignifying agents. They degrade by dissolution even
though some of them are readsorbed on the fibers. There
fore, optimization of a pulping process, in the chemical
sense, can be viewed as the retention of maximum amount of
cellulosic and hemicel lul.osic materials while dissolving
the required amount of lignin.
CMT and ECS can also be related to the hemicellulose
and lignin content of pulps. Different studies reveal that
ECS and CMT values are maximized at different yields
depending on the species and pulping methods. For a given
species at fixed pulping conditions, however, an optimum
yield point exists after which the two strength properties
remain almost unchanged. This is, indeed, an indication of
a critical lignin and hemicellulose content of a pulp at
which the two strength properties approach their ultimate
values.
For the strength loss degradation of cellulose should
be less important than the loss of hemicelluloses at high
yields because according to Jayme as stated by Cottral
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. (47), there exists a critical range of DP above which
strength properties are affected only marginally by
cellulose degradation.
Many researchers, in the past, have used freeness as
the refining variable and they prepared their hand sheets
at fixed freeness levels to compare the strength values at
different levels of pulping. However, this is not a
satisfactory method because it does not take into account
density and related thickness changes.
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. CHAPTER IV
PROBLEM STATEMENT
Sodium carbonate-sodium hydroxide high-yield pulping
of hardwoods for the production of corrugating medium has
been practiced in many U.S. pulp and paper mills since the
early 1970s. Even though straw is relatively easier to
pulp, this pulping method has never been used with straw
for corrugating medium production. The investigation of
sodium carbonate cooking of straw is of practical interest
because of the relative advantages of the chemical in the
recovery operation and on the environment.
In this experimental study, caustic fraction of the
cooking chemical and the cooking time were optimized with
respect to CMT and ECS while keeping temperature, liquor-
to-straw ratio, and total chemical charge constant. STFI
short span compressive strength test was chosen to deter
mine the ECS of the handsheets. The maximum strength
values that were obtained by sodium carbonate-sodium
hydroxide pulping were compared with the maximum values
obtained by pure sodium hydroxide pulping.
During the experiments, lignin and pentosan contents
of the pulps were determined. The correlation between the
chemical content of the pulps and their strength properties
38
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. were scrutinized.
The objectives of this experimental study were:
1. To optimize the pure sodium hydroxide cooking of wheat
straw at a fixed liquor-to-straw ratio and temperature with
respect to CMT and ECS.
2. To optimize the sodium carbonate-sodium hydroxide
cooking of wheat straw at a fixed liquor-to-straw ratio,
temperature and at the optimum total chemical charge found
for pure sodium hydroxide cooking with respect to CMT and
ECS.
3. To compare the sodium carbonate-sodium hydroxide and
sodium hydroxide semichemical pulping of wheat straw in
terms of strength properties and yield.
4. To make an attempt to correlate CMT and ECS values of
corrugating medium to pentosan and lignin contents of the
sodium carbonate-sodium hydroxide cooked wheat straw pulp.
39
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. CHAPTER V
EXPERIMENTAL DESIGN AND SCHEMATIC
Experimental Design
A rotatable central composite experimental design was
planned to find the maximum STFI and CMT values. The first
set of the composite design comprised a total of 6 cooking
experiments. The 6 experiments were set so that they
formed an orthogonal first order design with 2 center
points (Fig. 5). In the case of sodium carbonate-sodium
hydroxide pulping, there were 3 levels of cooking times and
three levels of caustic fractions, one from each being at
the center. Similarly, in the case of pure sodium hydrox
ide pulping there were 3 levels of cooking times and 3
levels of total chemical percent, one from each being at
the center. Natural variables were coded according to the
(-1 ,1)0 0 (1 ,1 )
0 ,0 )
(“1 , “1) O' o(l,-1 )
Figure 5. First Order Orthogonal Experimental Design.
40
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first order orthogonal design.
After performing the 6 experiments and measuring the
strength properties, a first order model of the form
was fitted to the data by using a first
order regression procedure. The adequacy of the model was
checked by applying analysis of variance. If the model
were found to be acceptable, the center point was moved to
another location to find a curvature on the response
surface. At that point, another first order model was
applied and its adequacy was checked. The procedure
continued as long as the data fit to the first order model.
Otherwise, 6 more experiments around that point were
performed and 6 more data points were added to the model.
The new design formed a composite second order model (Pig.
6).
(0,1.414) o
(-1 ,1)0-
(-1.414,0)0 0(1.414,0)
o(l,-1 )
o (0,-1.414)
Figure 6 . Composite Second Order Experimental Design.
Of the new 6 data points, 2 were at the center point
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 42
and the other 4 created another level which is necessary
for the application of a second order model. Analysis of
variance was applied to the second order model of the form
"y=(B(j+(Bi X1+32X2+P12X1 x2+^llxi^+f322x2^" :*‘n order to check the
closeness-of-fit.
Schematic
The cooks were made in 2 phases. The first phase
consisted of the pure sodium hydroxide cooks. The second
phase consisted of sodium carbonate-sodium hydroxide cooks.
The Tables 1 and 2 illustrate the cooking conditions that
were changed as per the statistical design explained
earlier.
1. Phase I. A total of 18 cooks were made changing
the cooking time and chemical percent on straw. One of the
aims for these cooks was to determine the optimum chemical
percent on straw. In all these cooks the cooking tempera
ture was maintained at 165°C and liquor-to-straw ratio was
maintained at 10:1. The optimum chemical charge on straw
was determined to be 6.5% (as Na20) from the phase I cooks.
2. Phase II. In all the phase II experiments, the
total chemical charge was maintained at the same 6.5% (as
NajO) . The variables in this phase of experiments were NaOH
fraction and cooking time at 165°C.
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 43
Table 1
Cooking Conditions in Phase I Cooks
Cook No. % Chemical on oven dry Cooking Time straw (as Na,0) at 165°C (min.)
3 6 60
5 8 30
6 4 30
7 6 60
8 4 90
9 8 90
10 6 60
11 6 60
12 8.828 60
13 3.172 60
14 6 17.58
15 6 102.42
16 4 30
17 8 30
18 5.5 17.58
19 7 17.58
20 6.5 17.58
28 6.25 17.58
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 44
Table 2
Cooking Conditions in Phase II Cooks
Cook No. NaOH fraction in the Cooking Time cooking liquor at 165°C (min.)
22 0.1 20
23 0.2 40
24 0.3 20
25 0.3 60
26 0.2 40
27 0.1 60
29 0.1 20
30 0.0 20
31 0.1707 34.144
32 0.1707 5.856
33 0.0293 5.856
34 0.0293 34.144
35 0.1 40
36 0.1 0
37 0.1 20
38 0.19707 20
39 0.1 20
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. CHAPTER VI
METHODOLOGY
In this study, the applicability of sodium carbonate-
sodium hydroxide semichemical pulping to straw for corru
gating medium production was tested on a laboratory scale.
Furthermore, the correlations between the lignin and
pentosan content of the pulp and related strength proper
ties were investigated.
The variables involved in the pulping experiments can
be divided into four categories:
1. Cooking control variables. (a) temperature (pres
sure), (b) time, (c) total chemical charge, (d) liquor-to-
straw ratio, and (e) composition of the cooking liquor.
2. Cooking response variables. (a) yield, (b) pento
san content of pulp, and (c) lignin content of pulp.
3. Refining control variables, (a) refining time, and
(b) refining load.
4. Refining response variables. (a) sheet strength
properties, (b) sheet density, and (c) fiber length
distribution.
Refining response variables are also related to the
cooking conditions. Therefore, strength properties are a
function of cooking and refining control variables.
45
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 46
In this study, the only refining control variable was
the refining level. Each pulp was beaten in the PFI mill
laboratory refiner at three different time spans.
Of the five cooking control variables listed, only
time and caustic fraction were varied for the sodium
carbonate-sodium hydroxide cooks whereas total chemical
charge and cooking time were varied for the sodium hydrox
ide cooks. The liquor-to-straw ratio (10:1) and tempera
ture (165°C) were fixed for all the runs.
The choice of variables was not arbitrary. As men
tioned in the literature review, temperature and chemical
concentration during cooking play an important role in
determining the carbohydrate loss. Thus, by fixing
temperature, liquor-to-straw ratio and total chemical
charge, the intention was to reduce the sources that cause
variation in carbohydrate degradation. Hence, in this
experiment, only caustic fraction of the chemical and
cooking time were responsible for the chemical composition
changes of the sodium carbonate-sodium hydroxide pulps.
Raw Materials
A thirty-eight pound bale of the main raw material,
soft, white, winter wheat straw (Triticum aestivum), was
purchased from Trowbridge township of Allegan County,
Michigan and was stored at 5% moisture in a sealed contain
er at ambient temperature prior to usage.
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 47
A long fibered base stock, to mix with the straw pulp,
was obtained fromMeijer Inc., Kalamazoo, Michigan, in the
form of grocery bags. These were repulped and mixed with
the straw pulps to the extent of 25% of the total stock.
The straw was cut to 2-3 in. long with a guillotine
cutter existing in the wood-working facilities of Western
Michigan University, Kalamazoo and was hand cleaned prior
to cooking to remove the grains.
Cooking and Washing
One hundred seventy six grams of oven dry (o.d.) straw
were cooked in the M & K digester with a liquor-to-straw
ratio of 10:1 and a preheating time of 35 ± 3 minutes. The
cooked straw was washed in tap water, centrifuged and then
disintegrated in a Waring blender at 1.5% consistency. The
pulp was then filtered, washed and centrifuged and stored
for further use in dark bags in a refrigerator at 4 3C.
The kraft bags were shredded and then soaked in
process water for 12 hours prior to defiberising in the
Valley beater at 1.57% consistency for 1 hour. The pulp
was then screw pressed, centrifuged and stored as in the
earlier case at 4°C. The pulp thus obtained was found to
have a freeness of 450 ml CSF.
Refining
The straw pulps were refined in a PFI mill at 10%
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 48
consistency in 21 g. batches for varying times to obtain
different sheet consistencies. It was also aimed that the
comparison of final strength property be made at a constant
density of 550 kg/m3. The pulps obtained from pure sodium
hydroxide cooks had to be refined for 30, 60 and 90 seconds
while the sodium carbonate-sodium hydroxide cooks needed
refining for a greater length of time (40-360 seconds).
Still, sheets made from some pulps did not achieve the
desired density of 550 kg/m3. This was in spite of the fact
that the freeness was low (190 ml) and the pulp took a long
time to drain in sheet formation operation. The same
phenomenon was observed in sodium hydroxide cooks too, when
chemical charge was low (3.172%).
Sheet Formation
The pulp from kraft bags was disintegrated in a
British standard disintegrator at 0.7% consistency for
15,625 revolutions (five minutes). Then it was mixed with
refined straw pulp in the ratio of 25:75, in the homogeniz-
er for 10 minutes at 0.14% consistency. Sheets were made
in Noble & Wood handsheet machine--existing in the Western
Michigan University Paper and Printing Science and Engi
neering Department's 1aboratories--from this homogenized
slurry so as to give sheets of 5.25 ± 0.05 oven dry grams
(127 g/m3). The sheets were pressed in the Noble & Wood
press and was dried with the steam heated cylinder in three
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 49
passes. The sheets thus obtained were kept in a precondi
tioning room held at 35% relative humidity and 72°F for 24
hours and then for 2 hours in the conditioning room held at
50% relative humidity and 72°F.
Determination of Strength Properties
From the handsheets, ten ”6 by 0.5 in." strips were
cut with Concora die-cutter for Concora tests and five "7
in. by 15 mm." strips were cut with TMI precision cutter
for STFI tests. The thickness and weight of each sample
were measured separately for density determination.
The strips were tested for the respective strength
properties by standard TAPPI procedures after suitably
calibrating the Concora crush tester and STFI short span
compressive strength tester. The Concora crush tester was
the one available in the Paper and Printing Science and
Engineering Department's paper testing laboratory at
Western Michigan University, Kalamazoo. The time on STFI
tester was donated by Green Bay Packaging Corporation,
Green Bay Wisconsin. The samples were taken to Green Bay D in Ziploc" bags and were conditioned once again for 12 hours
prior to testing.
For each individual pulp, various curves relating
strength property and density, strength property and
freeness, strength property and refining time and freeness
and refining time were constructed. With the help of these
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 50
curves, the relevant strength property values that meet
with chosen constraints of refining time, CSF, and density
were picked out for further statistical analysis.
Chemical Compositions of Raw Materials and Straw Pulps
The wheat straw, the straw pulp, and the kraft bag
pulp were all analyzed for pentosan content by standard
TAPPI procedures. The lignin content, however, was
estimated for straw pulp and kraft bag pulp by determining
the Kappa numbers. The conversion factors used in lignin
determination were 0.16 for straw pulp (16) and 0.15 for
kraft bag pulp (63). The lignin content was determined for
wheat straw by the standard method of Association Of
Agricultural Chemists. The method is enclosed in the
Appendix E.
The results of the raw material analysis are as
foilows:
1. Straw. (a) lignin content is 12.3%, (b) pentosan
content is 29.7%, and (c) ash content is 5.3%
2. Recycled Kraft Bag. (a) kappa number is 105, and
(b) pentosan content is 1 0 .2%.
All the determinations were made in duplicate and the
average values are reported. The standard error in the
estimates of lignin, pentosan and kappa number are 0.49,
0.52 and 0.90, respectively.
The various tests conducted, the standards followed,
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 51
and instruments used are listed in Table 3.
Table 3
Tests, Standards and Instruments
Test Standard Instrument
Processing of T 248 cm - 85 PFI mill Pulp
Processing of T 200 om - 85 Valley Beater Pulp
Freeness T 227 om - 85 Canadian Standard Freeness Tester
Forming Handsheets Noble & Wood for Physical Testing Handsheet Machine
Caliper In T 220 om - 88 TMI micrometer Physical Testing of Handsheets
CMT T 809 om - 87 Concora die-cutter, medium f luter & TMI crush tester
STFI T 826 pm- 86 LSW STFI compres sion tester
Preparation of T 264 om - 88 Wood for Chemical Analysis
Kappa Number T 236 cm - 85 of Pulp
Pentosan Content T 223 cm - 84 of Pulp
Ash content of T 211 om - 85 Wood
Lignin Content of OMA # 6.094 Straw
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. CHAPTER VII
ANALYSIS OP DATA
The objective of this study was to optimize the
Concora crush resistance and the STFI compressive strength
of the corrugating medium. Two kinds of cooks were made:
pure sodium hydroxide cooks and sodium carbonate-sodium
hydroxide cooks. For pure sodium hydroxide cooks, the
control variables were total chemical percent and cooking
time at 165°C; for sodium carbonate-sodium hydroxide cooks
control variables were cooking time at 165°C and sodium
hydroxide fraction in the cooking liquor. The optimum
total chemical percent for the Concora crush resistance
found for pure sodium hydroxide cooks was fixed for the
sodium carbonate-sodium hydroxide cooks.
A multi-step data analysis was used for the optimiza
tion study. The steps involved are listed below:
1. Six cooks were made as explained in the experimen
tal design.
2. The density of the strips from the 5.25 ± 0.1 g.
handsheets were determined.
3. Concora crush resistance and STFI values for each
strip were determined.
4. For each cook density vs. Concora and density vs.
52
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 53
STFI, graphs were drawn and regression lines were fitted.
5. The strength values at 550 kg/m3 were taken.
6 . With the 6 values obtained a multiple first order
regression analysis was carried out in order to determine
whether the region where the first six cooks were placed
had a curvature or not. First order regression and
analysis of variance were used for this purpose.
7. If analysis of variance revealed that the quadratic
terms are at least in the 10% confidence level, the second
order design was formed around the same center point.
Otherwise, the center point was carried to another point
and analysis continued until a curvature was found.
8 . A multiple second order regression analysis was
carried out by using the RSREG module of Statistical
Analysis Systems (SAS) software (64).
9. Canonical analysis was performed to determine the
location and the type of the stationary point. Canonical
analysis should give one of the three types of response
surfaces with the stationary point being a maximum, a
minimum, or a saddle point.
10. In those cases where a minimum or a saddle point
was found ridge analysis was carried out in order to locate
the maximum.
11. For the graphical representation of the response
surfaces GContour and G3D procedures of SAS-version 6
software package (64) available in the Vax system, WMU were
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 54
used.
Response Surface Methodology
Determination of Stationary Point Location
A second order model can be written in matrix notation
as follows:
Y = Bfl + x'b + x'Bx (16)
The derivative of Y with respect to the elements of the
vector x equated to 0 will give the stationary point:
~-jb+2flx-0 (17) dx
and,
Xo— j-B-t-b (18)
by substitution,
Y„ = Bfl + 1/2 xfl'b (19)
Characterization of the Response Surface
The stationary point could represent one of the
following: (a) a point of maximum response, (b) a point of
minimum response, or (c) a saddle point.
Even though the shape of the contour graph or the
three dimensional graph characterizes the response surface,
in some cases it is necessary to perform a mathematical
analysis which is called canonical analysis (65). The
model is first transformed into a new coordinate system
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 55
with the origin at the stationary point Xj and then the axes
of the new system are rotated until they are parallel to
the principal axes of the fitted response surface. The
equation of the model according to the new coordinate
system can be written as follows:
Y ,-y 0+A1W’12+*2wf (20)
where Aj and A2 are characteristic roots or eigenvalues of
the matrix B. The nature of the response surface can be
determined from the stationary point and the sign and
magnitude of the eigenvectors. When the stationary point
is within the region of exploration for fitting the second
order model, (a) the stationary point is a maximum if the
two eigenvalues are negative, (b) it is a minimum if they
are positive, and (c) it is a saddle point if they have
different signs. The surface is steepest in the w< direc
tion for which eigenvalue is the greatest. If one of the
eigenvalues is equal or close to zero, then the surface
represents a stationary ridge system. When the stationary
point is outside the region of exploration for fitting the
second order model and one of the eigenvalues is near zero,
then the surface may be a rising or falling ridge.
Ridge analysis computes the estimated ridge of optimum
response for increasing radii from the center of the
original design. The ridge analysis answers the following
question: "If there is not a unique optimum of the
response surface within the range of experimentation, in
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 56
which direction should further searching be done in order
to locate the optimum ?". The procedure consists of
formulating spheres with changing radii using the usual
coding of the variables, with the origin of the design at
(0 ,0 ), for a point (x^xj) on a sphere of radius R (66).
(21)
Application of Response Surface Methodology
Different constraints and relaxation of the density
requirement would give different results and assist to
investigate the problem from different angles. The two
constraints selected were the refining level and Canadian
Standard Freeness. For the optimization of Concora crush
resistance 90 second refining time was used as the con
straint .
After the screening experiments, six pure sodium
hydroxide cooks were done for the first order regression
analysis around the center point. Then, two more cooks at
the center point were added to better determine the pure
error. Conditions for these cooks were 6% total chemical
and 60 minutes cooking time at 165°C maximum temperature
(Fig. 7). The multivariate first order regression equation
for the first set of pure sodium hydroxide cooks with 550
kg/m^ density requirement and 90 second refining constraint
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 57
is given by equation 2 2 .
T 0 T A L 8% 8% 3 0 m i n 9 0 m i n . C H E 6% M 6 0 m i n . 1 C 4 % 4 % A 3 0 m i n 9 0 m i n . It
COOKING TIME AT 165°C < M I N . )
Figure 7. First Order Region for NaOH Cooks.
C0NC0RA (LBS.) - 60.1 + 0.394 C + 0.0072 T, (22)
where C is the total chemical charge (%) and T is the
cooking time at 165°C in minutes.
The ANOVA table for the regression model is presented
in Table 4. Since analysis of variance revealed that the
surface has a curvature, second order region was construct
ed around the same center point to carry out additional
cooks. The conditions are presented in Fig. 8 . The SAS
RSREG (64) analysis revealed that the response surface was
a saddle. Ridge analysis located the maximum response
point around the 6.5% total chemical charge and 18 minutes
cooking time at 165°C temperature.
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 58
Table 4
Analysis of Variance Table (Concora, First Order Regression, NaOH Cooks)
SOURCE OF VARIATION SS DF MS F0
REGRESSION 2.6700 2 1.335 0.23
RESIDUAL 5
INTERACTION 10.1442 1 10.1442 9. 92a
PURE QUADRATIC 16.3592 1 16.3592 15.99b
PURE ERROR 3.0693 3 1.0231
TOTAL 32.2430 7
* significant at 10% significant at 5%
T 0 T 8 . 8 2 8 % A 6 0 m i n £. 8% 8% C 3 0 m i n 9 0 m i n H E 6% M 6% ■ 6 0 m i n - 6% 1 17 . 58 m i n 1 0 2 . 4 2 m i n C A 4 % 4 % It 3 0 m i n 9 0 m i n
% 3 . 1 7 2 % 6 0 m i n
COOKING TIME AT 165°C (MINS.)
Figure 8 . Second Order Region for NaOH Cooks.
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 59
Therefore, four more cooks done at 5.5%, 6.25%, 6.5% and
7.0% total chemical charge were done by fixing the time at
17.58 minutes to locate the maximum more closely (Pig. 9).
7 5 -
2 7 0 -
6 5 -
5.5 CHEMICAL %
Figure 9. Verification of Maximum Found by SAS Analysis. Concora vs. Chemical Charge At 17.58 Minutes.
The following show the SAS statistical analysis and
the response surface obtained for the total number of 18
cooks (Table 5 and Figs. 10-12).
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. a\ o
0.0002 Prob > 0.0759 0.5158 0.0010 0.0003 3.920 0.448 12.451 17.799 13.105 F-ratio F-Ratio Prob > 4.753775 12.851475 Square 18.635547 0.8384 0.0060 0.3530 0.4794 Mean R-Square or At 90 Second Refining) 3 Table 5 5.762910 23.768875 154.217704 Squares 130.448829 457.490286 800.088141 Sum of 336.834945 of of Squares Type I Sum 5 7 2 2 1 Df Coef. Coef. of Variation 5.6168 Df R-Square 0.8384 Root MSE 3.584895 Response Mean 63.824444 Chemical Time 6.00 60.00 2.828 42.420 Factor Subtracted off Divided by 12 Coding Coefficients for the Independent Variables (At (At the Density of 550 kg/m Response Surface for Variable Concora: Concora Crush Resistance (lbs.) Pure Error Lack of Fit Total Error Linear Crossproduct Residual Quadratic Total Regression 5 Regression The SAS Statistical Analysis Concora for Data Set Pure of SodiumHydroxide Cooks
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 61
E4 fa A A VO CO at in 00 00 r- to • 00 © c~ o m to • o co A Ot o ino H r- A o VO O 00 o CM o m o O o o u • ■ • • • • U • • fa o o o © o o fa o o
r» to o o r> (0 at o 0 fa u e O U l O O M O U l O ft) co at co vo c** co 4 4 14 HOrt'fl'O Ot n> • ••••• E4 fa omntfoH i i i OtOt o in in r-4 ** ot ft) CM CM u O in Ot VO 00 CO r- ot d ft! • • T) vo Ot V 00 m -«*• m 9 co at U 00 CO r 4 r-4 CMCO ft) 0* m CO ft! CO i“4 [" Ot H S co r4 T) u r- Ot r-4 CO CM o d o vo CM CM CO O o ft! u • • • • ■ ■ 44 14 i n O o o o CO W r 4 00 VO CM t > m m< to co r~ 44 (1) r- oo O M o m u
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. to a\
. straw. % : Minutes :
Eigenvectors
(based on coded data) Stationary Point is a SADDLE point. Canonical Analysis of Response Surface Critical Value Predicted Value at Stationary Point 64.736101 0.196890 0.230848 6.556805 69.792590 Total Chemical Cooking on o.d Time at 165 °< Coded Uncoded 4.752500 -0.055912 0.998436 Eigenvalues Chemical Time -12.700455 0.998436 0.055912
Chemical Time Factor Table 5--Continued
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 63
o o o p> m CO in o co CO CN o rH CO vo CO O CO CO o CO cn o CO VO p» H in Ch cn 00 VO CN 01 o on 00 vo xP 00 CD m 00 CO p» 3 o CO ■O' xp rl CO
a ) 01 3 0 a ai 73o •i-i TJ xp P~ CN CO o XP O rH co 00 cn os 3 3 vo o CO vo CO rH m 00 Px o H 4-1 01 vo vo xp p- o xp VO o CO m cn 73 3 3 r"x P» xp O io XP O CO O in XP CO 4) 6 o • o cn CN cn in o co P> cn rH CN xp 00 CO px CO o Px in XP in VO 4-1 • r l a* oi • • • 3 4-1 VI S3 • • •••••• 73 cn o rH a > U1 3 xp xp m in VO p- p» CO £ VO VO VO vo rx E*** 3 W « x-r VO vo vo vo vo 3 3 O 0 1 I in 0 ) 73 3 3 rl Si T3 73 OrHCNcoxptnvop-cocno 3 O 3 O « ©OOOOOOOOOrH Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. a\ CHEHICXL *. TIMI HIM., CONCORA. U *. NaOH Cooks. CONCORA Figure Three10. Dimensional Representation of the SecondOrder ConcoraModel for Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. at Ui or m m CHEMICAL %, TIKI KIN., CONCORA CHCHICAL NaOH Cooks (Axes Are Rotated 90°). CONCORA Figure 11. FigureThree 11. Dimensional Representation theof SecondOrder ConcoraModel f Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Reproduced with permission of the copyright owner. Further reproduction prohibited w ithout permission. ithout w prohibited reproduction Further owner. copyright the of permission with Reproduced COOKING TIME-MIN. 120 Figure 12. Contour Plot of the Second Order Concora Model Concora Order Second the of Plot Contour 12. Figure 3 4 for NaOH Cooks. NaOH for 5 L A C I M E H C 6 X 9 7 71 70 66 67 A similar analysis was carried out for the sodium carbonate-sodium hydroxide cooks, with two cooks at the center point. The first order region was constructed around 40 minutes cooking time and 0.2 sodium hydroxide fraction (Pig. 13). N a 0 H 2 0 m i n 6 0 m i n F 0 . 3 £ 0 . 3 f R A 4 0 m i n C T 1 O 2 0 m i n 6 0 m i n N 0.1 f 0.1 f COOKING TIME AT 165°C (MINS) Figure 13. First Order Region for NajCOj-NaOH Cooks. The following equation was found for the first set of sodium carbonate-sodium hydroxide cooks with the 550 kg/vc? density requirement: CONCORA (LBS.) - 81.2 - 44.5 f -0.243 T, (23) where f is the NaOH fraction, T is the cooking time at 165°C in minutes. The analysis of variance data for the regression model are presented in Table 6 . Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 68 Table 6 Analysis Of Variance Table (Concora, First Order Regression, ^CO j - N a O H Cooks) SOURCE OF SS DF MS F0 VARIATION REGRESSION 173.70 2 86.85 7.53a RESIDUAL 3 INTERACTION 12.4256 1 12.4256 3068.06b PURE QUADRATIC 22.1680 1 22.1680 5473.58° PURE ERROR 0.0081 1 0.0081 TOTAL 208.29 5 * significant at 10% b significant at 5% c significant at 1% Because the pure error was too small, all terms, i.e., linear, quadratic, and interaction were found to be significant. Therefore, the center point was shifted to the point where sodium hydroxide fraction is 0.1 and the cooking time is 20 minutes (Fig. 14). That is the point where the maximum Concora value was obtained after the first set of experiments. The second order region was constructed without following the path of steepest ascent because the new center point was very close to the limits of the first quadrant of the analytical surface, and negative sodium hydroxide fraction and negative cooking Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 69 N a 0 H P R A . 1 9 7 0 C T . 1 7 0 7 1 O N . 1 0 Q O . 0 2 9 3 .OOOO O 5.85 20 34.14 40 COOKING TIME AT 165°C (MINS) Figure 14. Second Order Region for NajCOj Cooks. time do not have physical meanings. The SAS RSREG proce dure determines the response surface as a maximum when all 17 data points are taken into account. When only the second order region is considered, the response surface is a saddle. The maxima found depend on the constraint(s) and on the density requirement. Maxima also change when the whole region under investigation is taken into the consid eration rather than the second order region that was con structed around the second center point. The SAS analysis results for the last 12 sodium carbonate-sodium hydroxide cooks with 550- kg/m3 density requirement and 90 second refining constraint are presented in Table 7 and Figs. 15 and 16. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. o Prob > 0.0038 0.1957 0.0050 0.0031 0.0127 Prob > 57.426 2.119 9.873 11.439 17.665 F-ratio F-Ratio 0.345492 Square 19.840370 10.092931 0.5521 0.9051 0.3125 Mean R-Square Table 7 1.036475 60.557586 59.521111 21.390625 0.0335 Sum of Squares 577.281439 356.588980 of of Squares 199.301835 Type I Sum 6 3 3 5 1 2 Df 2 Coef. Coef. of Variation 4.7543 Df R-Square 0.9051 Response Mean Root MSE 66.822500 3.176937 Time 20.000000 20.000000 Factor Fraction Subtracted off 0.098535 Divided by 0.098535 of of Sodium Carbonate-SgdiumHydroxide Cooks Coding Coefficients for the Independent Variables The SAS Statistical Analysis for Concora Data Set (At (At the Density of 550 or kg/nr at 90 Second Refining) Response Surface for Variable Concora: Concora Crush Resistance (lbs.) I [ Lack of Fit Pure Error Total Error Residual Total Total Regression Crossproduct Linear Quadratic Regression Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Reproduced with permission of the copyright owner. Further reproduction prohibited w ithout permission. ithout w prohibited reproduction Further owner. copyright the of permission with Reproduced Table 7--Continued 44 -P a 04 04 44 44 •O V us X» E SC Oi EH A (8 (8 >4 Oi (0a £ V u ;o a; Li £ (8 £ « 3 18 0) 18 14 a> ■rl 44 CO CO Cn XP CN o rH in P* rH XP rH © o in CO CN CO P» CO 00 »CO P» m O o in OCO CO o xp >4 O o (8 a • • ■ • • • •H E in CO CO in CN rH rH m rH in in xp o cn rH O 00 00 o o CN £ a> O h • • 71 to - 4 Eigenvectors (based on coded data) Stationary Point is a SADDLE point. Canonical Analysis of Response Surface Predicted Value at Stationary Point 72.287282 Coded Uncoded 0.889631 0.989228 -0.146383 Eigenvalues Fraction Time ■14.846338 ■14.846338 0.146383 0.989228 Fraction 0.217232 0.119940 Sodium Hydroxide Fraction Time 0.210276 24.205520 Cooking Time Minutesat 165 °C Factor Critical Value Table 7— Continued Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 73 o CO Ot O CO o» N* CN m H rH o © in CO CO CO in O co 00 CO o o- CN 10 CO CO o O in r*- CO oi o in CO HP OO' co o m in CN 3 o © w r~ CN 00 CN in CO r- 00 3 0) o cn Ot 00 CO co o CO CO ot CN • •• ••*•• • • • < 0 '-I 6 U d ’H o rH CO N* in © co co CO CO r - o > ^ CN CN CN CN CN CN CN CN CN CN CN o a ti o o o 44 O 3 Rl H b C m ■N« m © o CO © CO SS rH CO VO ( 0 3 o CO o> at o o o CO r- •H 3 •H in rH CO CO 1—1O o* O 0 0 O' ij 00 at in rH © 0 0 r- r- CO CO © rH ( 0 at at Ol © CO in N* co CN o o o © o O o o O © o O o > • • • • • • • • • •• u EDa b o Q o o o o o o © o o 0 4H 3 01 c o 0 01 3 os e 3 CN CO o in o N* © CN CN © 3 Li O' CO CN o in rH CO© HP CO O' rH © in CN N* © © N* © s 3 COco 0-© rH O' O' © ■rl 3 >4 © o O r-l X C o © » © CO rH rH © © O' © 3 01 Li ■n in © in in in © © © rH © 4-1 Li • • • • • ■ • • • • • X W rH rH rH rHrH rHrH rHi—1rH rH 3 0 •a r H •rt 3 cn © © © N* © CN 00 r* os 3 3 © 'T © co © © 00 N* to r** 44 01 VC © © O' to O O' CN o CN as 3 3 3 V CO © HO © o © r H CN o © r* 3 e O • vo CN o r H CN to O' CN © O' r* CO HP © © O' as o CN 44 •rl CU 01 o • • • • •• m 44 01 £i • • • • ■ 3 cn cn a > 01 3 r H CN CN CNCN CN CN CN© £ Swuc O' O'O' 3 • w U OS O' O' O' C^ O' r- 44 . 3 01 U 3 o 0 1 I O' 0 ) 01 3 3 (1) H OHNfl'l'in'OMOO'O A ■3 *3 • •«••«••••• 3 O 3 Eh U OS OOOOOOOOOOrH Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Reproduced with permission of the copyright owner. Further reproduction prohibited w ithout permission. ithout w prohibited reproduction Further owner. copyright the of permission with Reproduced CONCORA w w i § B ^ m m i w f ■B&swwi&iwwWl < > '»<*> /'*" f/','"'A*&%r % I Figure 15. Three Dimensional Representation of the Second Order Concora Model for Na,CO,-NaOH Cooks. 74 Reproduced with permission of the copyright owner. Further reproduction prohibited w ithout permission. ithout w prohibited reproduction Further owner. copyright the of permission with Reproduced C00KIH6 T1HE-NIH 20 39 19 49 9 Figure 16. Contour Plot of the Concora ModelConcora the of Plot Contour 16. Figure 73.3 9.94 for NajCOj-NaOHfor Cooks. 9 • >99 iH FRACTIOH HiQH 75 CHAPTER VIII RESULTS AND DISCUSSION This study presents sodium carbonate pulping as an alternative to the sodium hydroxide pulping for the corrugating medium production from wheat straw. The two properties, Concora crush resistance and STPI short span compressive strength, are maximized by using both pulping methods in order to make a comparison. Response surface methodology is used as a tool in both cases. There are many studies in the literature (54, 57, 67) that optimize the pulping variables to obtain maximum Concora crush resistance and/or compressive strength values. However, in all those studies the problem was approached from a single point. In some studies, pulps were refined to a fixed low CSF (54, 67) and in some others, the density was kept constant (57). It is neces sary to fix the density or the CSF when chemical composi tions of pulps have to be studied to correlate them with possible strength development. In a mill, however, a mill manager is not interested in fixing the density of the medium nor is he willing to refine the pulp to a very low freeness in order to increase the strength properties. Rather, he is interested in 76 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 77 increasing the productivity of the paper machine. There fore, a plant manager has some limitations when making an optimization study. He has to effect refining constraints to keep the energy costs down and he needs freeness constraints to run the machine at its optimum speed. That is why pulping optimization studies done without taking these facts into the consideration do not lead to anything more than a better understanding of the subject. Because of the facts stated above, a finite constraint optimization study is needed. This envisages an optimi zation study that takes different constraints such as refining time and CSF into consideration. In the following pages, it will be shown how the maximum values for the response variables will change with the constraints imposed and the varying levels that they demand of the manipulated variables. Maximization of Strength Properties In pure sodium hydroxide cooks, total chemical percent on oven dry straw and cooking time at 165°C were optimized to obtain the maximum Concora crush resistance. A tempera ture of 165°C is chosen because the optimum temperature found by Lachenal, Wang, and Sarkanen (16) in sodium carbonate pulping of wheat straw was 160°C. The same authors also have found that the optimum total chemical charge in the first stage of a two stage Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 78 carbonate cook for bleachable wheat straw pulp is 3% (16). Therefore, in our study the first screening cook was made with 3% total chemical charge and one hour cooking time at 165°C. However, a very coarse pulp was obtained. Then, the location of the center point was moved to 6% total chemical charge and one hour cooking time at 165°C. The experimental steps were taken to be 2% for the total chemical charge and 30 minutes for the cooking time. Five different data sets (T1-T5) are generated for the maximization of Concora crush resistance with respect to total chemical charge and cooking time. Data sets differ from one another depending on the constraints applied. The T2 data set, for example, has a 550 kg/m^ density require ment and a 90 second refining constraint. The steps for the generation of the data set T2 are explained below: 1. A graph of Concora as a function of density was drawn from the linear regression equation generated from each cook. The spreadsheet prepared for the cook number 28 and the Concora vs. density graph drawn are shown in Table 8 and Fig. 17, respectively. 2. The Concora value at 550 kg/m^ density was computed from the Concora regression equation. The 69.4 lbs. Concora value found at the 550 kg/m^ density for the cook No. 28 from the regression equation is shown on Table 8 . 3. A graph of Concora and density as a function of refining time was generated by using the average Concora Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 79 Table 8 Concora Spreadsheet for Cook No. 28 Strip Weight Caliper Density Concora Concora No.______g.______pts.______kg/m3______lbs. Regression 30 sec. refining 1 0.263 10.20 524.5 64.0 64.4 2 0.263 10.16 526.6 60.0 64.8 3 0.266 10.36 522.3 68.0 64.0 4 0.265 10.42 517.3 65.0 63.0 5 0.262 10.16 524.5 67.0 64.4 6 0.266 10.08 536.8 63.0 66.8 7 0.270 10.18 539.5 68.0 67.4 8 0.270 10.34 531.2 65.0 65.7 9 0.267 10.22 531.4 64.5 65.8 10 0.263 10.22 523.5 64.0 64.2 60 sec. refining 1 0.263 9.26 577.7 75.0 74.8 2 0.265 9.38 574.7 73.0 74.2 3 0.269 9.54 573.6 75.0 74.0 4 0.265 9.22 584. 6 73.0 76.2 5 0.267 9.30 584.0 76.0 76.0 6 0.269 9.54 573. 6 77 .0 74.0 7 0.260 9.34 566.2 72.0 72.6 8 0.266 9.36 578.1 80.0 74.9 9 0.270 9.40 584.3 73.0 76.1 10 0.263 9.50 563.1 73.0 72.0 90 sec. refining 1 0.265 8.92 604.3 84.0 80.0 2 0.267 9.26 586.5 78.0 76.5 3 0.267 9.16 592.9 75.0 77.8 4 0.264 9.18 585.0 75.0 76.2 5 0.266 9.20 588.1 80.0 76.9 6 0.266 9.16 590.7 76.0 77.4 7 0.266 9.06 597.2 73.0 78.6 8 0.266 9.14 592.0 74.5 77.6 9 0.267 9.10 596.8 84.0 78.6 550.0 69.4 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 80 Table 8--Continued Concora Regression Output: Constant -37.995 Standard Error of Y Estimation 2.95661 R Squared 0.79 No. of Observations 29 Degrees of Freedom 27 X Coefficient 0.195276 Standard Error of Coefficient 0.019432 too 95- 90 85- 80- B o 00- 50- 45- 40- 30 DENSITY (K g /m J ) Figure 17. Concora regression Line for Cook No. 28 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 81 and density values at the specific refining times (30, 60 and 90 seconds) (Fig. 18). 640 620- ■85 600- 580- ■75 540- 500- ■60 •56 ■50 440- 420- 400 30 80 30 GOHCORA Figure 18. The Change of Density and Concora with Refining Time 4. If the 550 kg/rn^ density could not be reached in 90 seconds, the Concora value corresponding to the average density at 90 second refining time was taken. 5. The Concora values of all the 18 pure sodium hydroxide cooks were calculated in a similar fashion and the T2 data set was generated. Other data sets were generated in a similar manner with some minor differences in the procedure according to the constraints applied. For example, the T5 data set has both 90 second refining and 300 ml CSF constraints but does not have a density requirement. Hence, the generation of Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 82 the T5 data set was slightly different than that of the T2 data set. The Concora values were calculated at 90 second refining time unless the freeness values were lower than the 300 ml CSP. If the pulp reached the 300 ml CSP in 90 seconds or less, the Concora value was calculated at 300 ml CSF. For that reason, a graph of density and Concora as a function of CSF was generated (Fig. 19). 620 -as B00 ■80 •75 •70 3 520 500 -55 450 440 420 -45 -420 -400 -580 -360 -340 -320 -300 -280 CSF (ML) C0KC0RA Figure 19. The Change of Concora and Density With CSF. In the data sets T1 to T5, the response surfaces obtained were of saddle type and the maxima were found by ridge analysis. The summary of statistical analyses for these data sets is presented in Table 9. The data show a 4 to 5 lbs. increase in Concora values when the density requirement is eliminated. Concora values increase again Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Id 03 66 166 Time (sec. (%> 62.5 Max.Pt. 77.10 53.9 90 77.55 53.8 90 72.40 73.29 63.4 180 (lb.) 4.91 6.56 71.63 56.8 4.68 18.43 22.45 (min.) % Table 9 Hydroxide Cooks Saddle 99.15 7.09 Saddle Saddle Stat.Pt. (lb) 75.02 Saddle 99.49 7.03 64.73 63.83 Stat.Pt 90 90 No No No 1 No 90 75.50 1 , : , : at 550 300 No 64.42 Saddle 20.85 550 Summary of the Statistical Analysis for Concora Data Sets of Pure Sodium (kg/m3) (ml) (sec) (ml) (kg/m3) T4 No T5 No 300 T2 T3 Set Set Dens. CSP Ref. Concora of Cook.Time Chem.Value Yield at Ref. T1 550 Data Constraints Predicted Type Max.Response Max.Concora Predicted Max.Pt Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. when refining constraints are relaxed. Two distinct levels of optimum cooking time were found depending on whether the density requirement was applied or not. When there was 550 kg/m* density requirement, the optimum cooking time remained fixed around 20 minutes even though the constraints were changed. When a 90 second refining constraint was applied, the optimum chemical charge rose from 4.68%--obtained in non-constrained case--to 6.56%. A CSF constraint of 300 ml did not change the optima of controlled variables--cooking time and chemicals %— since most of the pulps under the region investigated reached the 550 kg/m* density without crossing the freeness limits. On the other hand, when the density requirement was eliminated the optimum cooking time shifted to around 100 minutes and the optimum total chemical charge was found to be 7%. In sodium carbonate- sodium hydroxide cooks, cooking time at 165°C and NaOH fraction in the sodium carbonate-sodium hydroxide cooks were optimized with respect to Concora crush resistance. Table 10 illustrates the fourteen data sets that were generated for this purpose. Seven of the sets, TA1 to TA7, comprise the region under 0.0 to 0.3 NaOH fraction and 0 to 60 minutes cooking time. These sets are the result of all the 17 cooks. They were generated in order to identify the overall picture of the experimental region, but they were not used to obtain the specific Concora values and the optimum values for the controlled variables. All the Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Ol CD 78 104 114 112 214 Time (sec. 64.3 92 64.1 64.4 98 (%> Max.Resp. 71.7373.55 63.6 73.88 64.9 72.68 65.5 150 72.01 73.4171.52 65.4 61.8 134 63 73.37 67.3 (lb.) 0.0400 0.0000 0.0120 0.0070 73.48 63.8 0.0016 Frac. 6.50 0.0160 21.35 14.20 22.61 0.0008 73.80 19.61 Time (min.) Table 10 Saddle 23.81 0.0018 Saddle Maximum Maximum Maximum99 19. 0.0270 Stat.Pt (lb) 71.42 71.73 70.86 Saddle 72.68 72.01 71.52 Maximum 31.31 0.0670 Stat.Pt Sodium Carbonate-SodiumHydroxide Cooks No 90 72.23 Saddle 27.28 No -4.26 Saddle 16.38 No 73.37 Maximum 270 180 71.31 No 270 No 90 300 300 No 300 Summary of the Statistical Analysis for Concora Data Sets of , , at 550 550 300 180 550 No 550 550 No (kg/m3) (ml) (sec) (ml) (kg/m3) TAL5 550 TAL4 550 TA5 550 TAL3 *A4 550 No TA3 TAL2 TA2 TALI 550 No TA1 Set Set Dens. CSF Ref. Concora of Cooking NaOH Value Yield at Ref. Data Constraints Predicted Type Max.Response Max.Concora Predicted Max.Pt Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 90 (sec . Tin . 61.2 90 61.0 90 60.7 (%) Max.Resp 74.31 (lb.) 0.0940 76.76 0.1200 Frac. 23.58 0.1950 78.86 61.1 90 24.15 0.1950 76.81 Time (min.) Maximum 31.67 Stat.Pt Maximum 32.46 76.43 Saddle 76.76 74.31 (lb) Stat.Pt at 90 74.23 Saddle 90 120 120 ec) 300 No No No No 6 (kg/m3) (ml) (s (ml) (kg/m3) 6 TAL7 No 300 TA7 No TAL Set Set Dens. CSF Ref. Concora of Cooking NaOH Value Yield at Ref. TA Data Constraints Predicted Type Max.Response Max.Concora Predicted Max.Pt Table 10--Continued Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 87 response surfaces for these data sets are in the shape of maximum. Also, all the data sets locate the maximum in the second order region that was created by the last 12 sodium carbonate-sodium hydroxide cooks. The other seven sets, TALI to TAL7, comprise the cooks belonging to the second order region alone under 0 to 0.2 sodium hydroxide fraction and 0 to 34 minutes cooking time at 165°C. All the response surfaces are in the form of saddle and the maxima are found by ridge analysis. All of the maximum Concora values are found to be in the 73 to 74 lb. range, regardless of the constraints used when 550 kg/m^ density requirement is imposed. The optimum sodium hydroxide fractions are lower than 0.01 in each case. The optimum cooking time decreases with the relaxations in the constraints. For the data set TAL2 with 90 second refining time, the optimum cooking time was found to be 27.28 minutes and the optimum sodium hydroxide fraction 0.007. On the other hand, when the density requirement is elimi nated, the optima shift from 0.00-0.01 to 0.195 sodium hydroxide fraction while the cooking time decreases slightly. Again, the nominal Concora values are 3 to 5 points higher for the data sets which do not have the density requirement. The 0.195 sodium hydroxide fraction is almost equal to the optimum 0.2 sodium hydroxide fraction found for hardwoods by Hanson and Kukolich (67). However, they used Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 88 10% total chemical charge, 40 minutes cooking time and they refined the pulps to 200 CSF without any density require ment when obtaining the 0.2 optimum fraction. The STFI values of the handsheets prepared during the optimization of Concora crush resistance were also checked. However, extra cooks to locate the maximum STFI have not been made. Therefore, control variables were optimized for STFI short span compressive strength around the same regions investigated for the optimization of Concora crush resistance. The maximum values were found by ridge analysis in most of the data sets. In pure sodium hydroxide cooks, a total of five data sets, TS1 to TS5, were generated for the optimization of pure sodium hydroxide cooks for STFI. The summary of the statistical analysis conducted for these data sets is presented in Table 11. The data sets were generated in a similar manner as in the case of Concora crush resistance. The only difference was that Concora values were replaced by STFI values and regression lines and graphs were generated accordingly. Two of the data sets depict the response surfaces as maxima, two of them as minima, and one of them as a saddle. The maximum STFI values for the four data sets, TS1, TS3, TS4 and TS5 are almost the same, i.e., 26.00-26.83 lbs/in. The maximum STFI value for the data set with 90 second refining constraint and density of 550 kg/m3 (TS2) was Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. co CD 90 212 223 Time Ref. Max.Pt (sec.) (%) 53.8 90 68.3 53.7 68.5 56.6 19 Predicted Yield at Max.Resp. 24.65 (lb/in) Max.STFI Value 3.17 26.00 3.19 26.25 59.07 7.49 26.83 55.04 (min.) (min.) % Table 11 Hydroxide Cooks Saddle 102.13 5.67 Minimum 59.72 Maximum of of Stat.Pt. Cook.Time Chem. Type Max.Response 26.70 Maximum 59.50 7.40 26.70 23.50 Stat.Pt. STFI STFI at (lb/in) Predicted 90 No No 22.37 Minimum 300 550 No 90 Constraints Summary of the Statistical Analysis for STFI Data Sets of Pure Sodium Dens. Dens. CSF Ref. (kg/m^) (ml) (sec) (ml) (kg/m^) TS4TS5 No No No 90 26.84 TS3 550 300 No 22.03 TS2 Set TS1 550 Data Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 90 slightly lower than the others (24.65 lbs/in.). In a similar fashion, the optimum cooking times were very close for the previously mentioned four data sets, from 55 to 60 minutes). For the data set TS2, the optimum cooking time was almost twice as long (102 minutes). The optimum chemical percentages for the data sets with the density requirement were lower than the optimum chemical percent ages for the data sets without density requirement. The data sets with density requirement and without constraints or with 300 ml freeness constraint located the optimum chemical charge at around 3.2%. With density requirement and 90 second refining constraint, the optimum chemical percent shifted to 5.7%. When the density requirement was eliminated, the optimum shifted to 7.5%. Overall, higher cooking times are necessary to maximize the STFI short span compressive strength as compared to the Concora in the presence of density require ment. Also, the STFI is maximized at lower chemical percentages than Concora. For the data sets where density requirement is eliminated, optimum cooking times are lower for the STFI than Concora, but optimum chemical percentages are slightly higher (+ 0.4%). In sodium carbonate-sodium hydroxide cooks, a total of fourteen data sets were generated for the maximization of STFI. Again, as in the case of optimization for Concora, the seven data sets, TAS1 to TAS7, were created to show the Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 91 response surface in a larger data map. All these data sets locate the optimum values in the second order region. The other seven data sets, TASL1 to TASL7, were created to find the maximum response and optimum values for sodium hydrox ide fraction and cooking time in the second order region. All of the seven data sets belonging to the second order region exhibit saddle response surfaces. Maximum STFI values were found in the region of 25 to 27.5 lbs/in. The summary of the statistical analyses for these data sets are presented in Table 12. The first five data sets, TASL1 to TASL5, had the density requirement. For the non-con- strained data set, the optimum was found around 2 minutes cooking time and 0.060 sodium hydroxide fraction. As the refining was decreased, i.e., from 270 seconds to 180 seconds and then 90 seconds, the optimum cooking time in creased while the optimum sodium hydroxide fraction decreased. Finally, for the data set with 90 second refining constraint (TASL2), optimum values were found to be 26 minutes and 0.004 sodium hydroxide fraction. These values were close to the optimum values found for the Concora data set (TAL2) with density requirement and 90 second refining constraint, i.e., 27 minutes and 0.007 fraction. However, when the density requirement was eliminated, the optimum sodium hydroxide fraction shifted to 0.19 similar to the case of Concora optimization. Optimum cooking time was found as 27 minutes. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. ID to 84 221 264 261 Time (sec 67.867.2 269 67.1 219 63.6 58 67.9 67.7 270 (%) Max.Resp. 25.73 25.72 26.52 67.4 234 26.10 67.6 25.79 67.7 270 25.18 64.0 (lb/in) Frac. 0.0367 0.1540 0.1290 26.64 5.72 0.0296 4.43 1.00 0.1120 0.01 5.93 0.0285 26.00 1.70 0.0587 27.04 25.73 0.0040 34.66 0.0018 25.24 (min.) Table 12 Saddle Saddle Minimum Minimum Minimum 0.29 0.1290 Saddle Stat.Pt Time Minimum 0.30 25.20 Saddle 22.12 24.81 20.99 24.94 23.55 Stat.Pt (lb/in) Sodium Carbonate-SodiumHydroxide Cooks No 19.83 270 24.40 Saddle 270 180 ec) No 90 300 No Summary of the Statistical Analysis for STFI Data Sets of 550 300 550 No 550 300 550 300 180 550 550 No 90 24.26 Saddle (kg/m3) (ml) (s (ml) (kg/m3) TASL5 550 TAS5 TASL4 TASL3 TAS4 550 No TASL2 TAS3 TASL1 550 No No TAS2 TAS1 550 No No 22.53 Set Set Dens. CSF Ref. STFI at of Cooking NaOH Value Yield at Ref. Data Constraints Predicted Type Max.Response Max.STFI Predicted Max.Pt Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 1 0 CO 90 60.5 60.559.9 90 90 59.8 90 Predicted Max.Pt Max.Resp. Time 27.13 27.32 26.57 26.88 Value Yield at Ref. Max.STFI (lb/in) (%) (sec.) 33.67 0.2990 27 .72 27 0.1890 27.29 0.1900 Cooking NaOH Time Frac. (min. ) (min. Saddle 34.65 0.2980 of 27.03 Saddle 26.91 Saddle 25.78 Stat.Pt Stat.Pt STFI STFI at Predicted Type Max.Response (lb/in) 90 25.89 Saddle 120 120 No No 90 300 No No No 6 (kg/m3) (ml) (sec) (ml) (kg/m3) 6 TASL7 TAS7 NO 300 TASL Set Set Dens. CSF Ref. TAS Data Constraints Table 12— Continued Reproduced with permission of the copyright owner. Further reproduction prohibited without permission 94 Pulp Yield and Its Correlation With Strength Properties Application of different chemical percentages, chemical compositions, and cooking times generated pulps with different yields. Two data sets, one for pure sodium hydroxide cooks, and another one for sodium carbonate- sodium hydroxide cooks were generated in order to find the relationship between the cooking variables and the yield. The response surfaces are depicted by Pigs. 20 and 21. The two regression equations (Eqs. 24 and 25) for pure sodium hydroxide and sodium carbonate-sodium hydroxide cooks that were generated by the SAS RSREG procedure are illustrated below: 1. Pure sodium hydroxide cooks, Yield=96.4593 - 8.8265 Chem. - 0.1279 Time + 0.4431 Chem.2 + 0.0002 Time2 + 0.0123 Time*Chem. (24) The R‘ and F probability values for the regression are 0.94 and 0 .0 0 , respectively. 2. Sodium carbonate-sodium hydroxide cooks, Yield=69.5788 - 22.3345 Fract - 0.3300 Time + 69.5817 Fract2 - 0.3292 Time*Fract + 0.0046 Time2 (25) The R2 and F probability values for the regression are 0.70 and 0 .0 1 , respectively. From the above regression equations the yields at the optimum cooking variables corresponding to the maximum Concora and STFI values were calculated. Pulp yields at maxima also changed depending on the Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. io Ul IIU> x .>. .>. mxm < cHiincu. («i. Tin («i. cHiincu. , x o m * t » data NaOH Cooks. YZSLO 96.46 H Figure 20. Three Dimensional Representation of the Second Order YieldModel for Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 96 a i a i x Reproduced with permission ofthe copyright owner. Further reproduction prohibited without permission. 97 constraints and the density requirement. During the optimization of Concora for pure sodium hydroxide cooks, the maximum Concora value was reached at 63.4% yield with density requirement and without any constraint. The 90- second refining constraint caused a 6 .6% yield decrease. Without the density requirement, the refining constraint of 90 seconds, resulted in a still lower yield of 54% at the Concora maxima. This drop was due to the higher chemical charge and longer cooking times needed to maximize Concora. During the optimization of Concora in the sodium carbonate-sodium hydroxide cooks, the yield values at the maxima are 2 to 5% higher than the values found at the maxima of pure sodium hydroxide cooks. When the density requirement is eliminated, the yield values at the maxima drop from 64-65% to 61%. During the optimization of STFI for pure sodium hydroxide cooks, the yield values at the maximum was found as 68.5% when there were no refining constraints. The 90- second refining constraint caused a yield decrease of 12 percentage points to 56.6%. Eliminating the density requirement caused another 3 percentage point decrease to 53.7%. During the optimization of STFI for sodium carbon ate-sodium hydroxide cooks, the yield values show a similar trend as in the case of pure sodium hydroxide cooks.' However all the yield values for STFI maxima are approxi mately 2 points higher than the yield values for the Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 98 Concora maxima where there is no density requirement. If density constraints were imposed, there was no significant difference in the yield values. The correlation between the yield and the strength properties is presented in Figs. 22-25 for three selected data sets each, for both types of cooks, and both strength properties. Each figure illustrates the relationship between yield and the strength property subject to differ ent constraints for the given cooking method. The strength properties increase with yield when there are no refining constraints. This is due to the longer refining time needed for coarser pulps to reach the 550 kg/rn^ density. When all the pulps are compared at the same refining level,the strength properties increase with decreasing yield. However, the rate of increase is lower after a plateau is reached. The plateau is reached at a higher yield for COncora than the STFI. When both density requirement and refining constraint are applied, the curve obtained is a combination of the other two. There exists a maximum on this curve. At low yields the strength properties are low since the pulps reach the 550 kg/m^ density level at short refining times whereas at high yields the pulps can not reach the density before the constrained refining time. In practice, refining time as a constraint is operative only at yield values beyond 63- 65% (Figs. 22-25). Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 99 85 80- T4 75- 65- T2 55- 50- T1 : 880 kg/nrv3 density, no oonstralnta T2 i 830 kg/m8 density, 90 esc. rstlnlng constraint 45- TA : No dsnstty rsqulramsnt, a t 9 0 use, refining 40 50 52 54 5$ 58 60 62 64 66 68 70 YIELD % Figure 22. Concora vs. Yield, NaOH Cooks. 85 80- 75- TA1 TA6 65- TA2 55- 50- TA1 : 5 3 0 k g /m 3 , no constraints TA2 : 3 50 k o /m 3 , SO esc. roffhlng constraint 45- TA6 no density rsg jlrsm sn t at 9 0 ssc.rotlnlno 40 58 60 62 64 66 68 70 72 YIELD % Figure 23. Concora vs. Yield, NajCOj-NaOH Cooks. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 1 0 0 28 TS4 TSI 24- TS2 tn 2 0 - TS1 ; 530 kg/m3 daralty, no constralhtE TS2 : 550 k g / m S dsnslfy, 90 sue. rflfTnfng aonstrafnt T34 i no danalty f g u lr t ia r r t . ot 90 BOO. r« 50 52 54 56 58 60 62 64 66 68 70 YIELD % Figure 24. STFI vs. Yield, NaOH Cooks. 28 TAS6 26- TAS1 24- TAS2 2 0 - TAS1 i 550 Irg/m S dam lty, no con*1poiof* TAS2 i 550 k g / m3 d tra ity , 9 0 aoo refining constraint TASS i no donefly raqutrBment, at SO coa raffning 58 60 62 64 66 68 70 72 YIELD % Figure 25. STFI vs. Yield, NajCOj-NaOH Cooks. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. The Relationship Between Concora and STFI Figs. 26 and 27 show that there exists a positive T2-TS2 T1-TS1 T H S 4 2 \ m j i l h W T 1 - I S I : 550 kg/m3, no constraints T2-TS2:5 5 0 kg/m3, 90 set refining consiroint T4-T54: to densjiy requirement, at 90 sec, retinfnq 55 60 65 70 75 CONCORA (LBS.) Figure 26. The Relationship Between Concora and STFI (NaOH Cooks). Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 1 0 2 linear relationship between the Concora and STFI values £or different constraints. The regression equations, the ANOVA tables, and coefficient of determinations are shown TA6-TAS5 TA1-TAS1:5 5 0 kg/m3 density, no conslrdnls T A H A S 2 :5 5 0 kg/mJ density, 90 sec. refining consfrdni 21 - TA6-TAS6: no density requirement, d 90 sec, refining 20 5 5 6 0 6 5 7 0 7 5 CONCORA (LBS.) Figure 27. The Relationship Between Concora and STFI (Na2C03-Na0H Cooks). Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 103 in Tables 48 to 53, in Appendix C. The slopes of regres sion lines for each strength property are close for the two cooking methods investigated. F probabilities for the first order linear model are in the 5% confidence level. Chemical Composition of Pulps Tables 13 and 14 represent the change of chemical composition as a result of altering cooking conditions. Table 13 Change in Chemical Compositions With Cooking Conditions (Pure Sodium Hydroxide Cooks) CK. KAPPA YIELD LIGN. LIGN. PENTSN . PENTSN t o t a l " ON ON ON ON LIGN. PENTSN. PULP STRAW PULP STRAW # # % % % % % % % 06 87.0 6 6 . 6 13.9 9.3 25.7 17.1 14.4 21.8 08 103.0 61.8 16.5 10.2 23.5 14.5 16.3 20.2 09 53.4 54.3 8.5 4.6 27.4 14.9 10.3 23.1 11 74.0 56.5 11.8 6.7 25.0 14.1 12.8 21.3 12 36.9 51.6 5.9 3.0 29.1 15.0 8.4 24.4 13 101.0 69.9 16.2 11.3 25.4 17.8 16.1 21.6 15 73.1 55.2 11.7 6.5 26.4 14.6 12.7 22.4 16 90.8 64.2 14.5 9.3 27.2 17.5 14.8 23.0 20 60 .8 58.4 9.7 5.7 28.2 16.5 11.2 23.7 * Lignin in straw, raw material is 12.3 g per 100 g of straw, pentosan in straw, raw material is 29.7 g per 100 g of straw ** Total Lignin and pentosan in mixed pulp (straw+recycled) Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 104 Table 14 Change in Chemical Composition With Cooking Conditions (Sodium Carbonate-Sodium Hydroxide Cooks) CK. KAPPA YIELD LIGN. LIGN. PENTSN. PENTSN. TOTAL ON ON ON ON LIGN. PENTSN. PULP STRAW PULP STRAW # # %%%%%% % 24 80.3 63.5 12.8 8.1 26.7 17.0 13.5 22.6 29 83.8 62.2 13.4 8.3 28.1 17.5 14.0 23.6 30 84.2 63.9 13.5 8.6 26.7 17.1 14.1 22.6 31 85.8 60.9 13.7 8.3 27.0 16.4 14.2 22.8 32 82.4 61.7 13.2 8.1 -■ - 13.8 - 33 80.5 67.7 12.9 8.7 26.8 18.1 13.6 22.7 34 85.7 62.9 13.7 8.6 25.7 16.2 14.2 21.8 35 82.7 60. 6 13.2 8.0 26.3 15.9 13.8 22.3 36 82.3 70.9 13.1 9.3 28. 6 20.3 13.8 24.0 38 78.2 62.1 12.5 7.8 26.1 16.2 13.3 22.1 * Lignin in straw, raw material is 12.3 g per 100 g of straw, pentosan in straw, raw material is 29.7 g per 100 g of straw. ** Total lignin and pentosan in mixed pulp (straw+recycled) As shown by the two tables, the amounts of undissolved lignin and pentosan and their relative proportions were different for each pulp. The correlation between the cooking variables and the lignin and pentosan contents of the pulps was also investi gated. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 105 Five data sets, as described in Table 15, were generated as a result of lignin and pentosan determinations in straw, straw pulp, and mixed pulp (straw pulp + recycled fiber) for both sodium hydroxide and sodium carbonate- sodium hydroxide cooks. Table 15 Nomenclature for the Data Sets That Correlate the Cooking Variables to the Chemical Composition of Pulp Particulars Names of Data Sets NaOH Cooks Na2C03~Na0H Cooks Kappa No. of Straw Pulp Kappal Kappa2 Lignin % on o.d. Straw Ligretl Ligret2 Lignin % in Mixed Pulp TLP1 TLP2 Pentosan % on o.d. Straw Pentretl Pentret2 Pentosan % in Mixed Pulp TPP1 TPP2 The Kappal data set shows the change in kappa number depending on total chemical charge and cooking time at 165°C for pure sodium hydroxide cooks. The contour graph of the Kappal data set (Fig. 28) depicts a decreasing ridge. The Kappa number is more sensitive to the changes in total chemical charge than the changes in cooking time. An increase in cooking time, at the same chemical charge, does not cause a decrease in kappa number. However, yield values continue to decrease with increasing cooking time. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 2 cHEttlCAV- V. ' Figure 28- = — “ Gras 107 This suggests that, at increased cooking times, cellulosic material dissolves faster than lignin and/or condensation reactions become more effective as presented earlier by Lachenal, Wang and Sarkanen (16). The Ligretl data set correlates the change in remain ing lignin percent on oven dry straw to the cooking variables (Table 15). The contour graph of the data set (Pig. 29) exhibits a similar qualitative relationship with the cooking variables. Shorter cooking times with higher chemical percentages lead to lower lignin retention. The Penretl data set (Table 15) illustrates the change in remaining pentosan content. This data set is presented in Fig. 30 in the form of a contour graph. The figure shows that remaining pentosan percent on oven dry straw drastically decreases with increasing cooking time. The increase in total chemical charge also causes more pentosan dissolution as expected. As a result, by looking at the contour graphs of Kappal, Ligretl, and Penretl, together, it can be concluded that a higher cooking time does not help delignification much, but causes more dissolution of hemicellulosic materi al . The Kappa2 data set shows the change in kappa number depending on sodium hydroxide fraction and cooking time at 165°C for pure sodium carbonate-sodium hydroxide cooks. The Kappa2 contour graph shows a similar trend as the Kappal Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Reproduced with permission of the copyright owner. Further reproduction prohibited w ithout permission. ithout w prohibited reproduction Further owner. copyright the of permission with Reproduced COOK IH6 TIME-HIN 100 iue 9 CnorGah f irt Dt Set. Data Ligretl of Graph Contour 29. Figure 8 2 4 CHEMICAL 2 6 8 10 108 109 Z HiI as m m CD O ou 8 2 4 8 18 CHEMICAL X Figure 30. Contour Graph of Penretl Data Set. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 1 1 0 for the changes in cooking time (Fig. 31). The kappa number increases with the rising cooking time. This again indicates two possibilities. The dissolution of hemicellu- losic material is faster than lignin and/or lignin conden sation reactions becomes more effective when the cooking time increases. The Ligret2 data set shows the remaining lignin in pulp with the change in cooking time and sodium hydroxide fraction. At elevated temperatures, lignin dissolution is higher for the pulps cooked .with higher sodium hydroxide fractions (Fig. 32). The Penret2 data set (Table 15) correlates the change in pentosan percent on oven dry straw to the NaOH fraction and cooking time at 165°C. Remaining pentosan percentage decreases with increasing cooking time. This decrease of remaining pentosans stabilizes after 20-25 minutes cooking time for the low sodium hydroxide fractions (Fig. 33). However, the decrease continues for high sodium hydroxide fractions. At low cooking times, i.e., from 0 to 20 minutes, pulps cooked with higher sodium hydroxide fraction have slightly lower pentosan dissolution (Fig. 33). Sodium hydroxide is more active than sodium carbonate. At the beginning of the cook, most of the alkali is spent for the neutralization of organic acids. Therefore, one can conclude that sodium hydroxide is more efficient than sodium carbonate for the neutralization of acids. On the Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Reproduced with permission of the copyright owner. Further reproduction prohibited w ithout permission. ithout w prohibited reproduction Further owner. copyright the of permission with Reproduced C00KIN6 TIME-HIN iue 1 CnorGaho Kpa Dt Set. Data Kappa2 of Graph Contour 31. Figure 8 0. 83 8 N a O HFR A C T IO N 8.13 8.2 . 58.3 8.25 1 1 1 Reproduced with permission of the copyright owner. Further reproduction prohibited w ithout permission. ithout w prohibited reproduction Further owner. copyright the of permission with Reproduced COOK IHS T1HE-HIH iue 2 CnorGaho Lge2 aa Set. Data Ligret2 of Graph Contour 32. Figure e 0.05 H iO HF R A C T IO N 8.25 2 1 1 Reproduced with permission of the copyright owner. Further reproduction prohibited w ithout permission. ithout w prohibited reproduction Further owner. copyright the of permission with Reproduced COOKING TIHE-HIN. e Figure 33. Contour Contour 33. Figure 6.65 6.1 aH FRACTION NaOH h p a r G 6.15 f ert Dt Set. Data Penret2 of 6.2 8.25 8 .3 113 114 other hand, remaining sodium hydroxide could attack hemicelluloses more easily when the cook proceeds and could cause their degradation. Relevant statistical analysis, development of regres sion equations used in contour and surface mapping of these data sets, and summary of canonical and ridge analyses are presented in Appendix B. The Relationship Between Chemical Composition of Pulp and the Strength Properties For pure sodium hydroxide cooks, a iotal of twelve data sets were generated in order to determine the rela tionship between the strength properties and the chemical compositions of the pulps. In a similar fashion, another twelve data sets were generated for the sodium carbonate- sodium hydroxide pulps. The nomenclature and details of these data sets are listed in Table 16. The chemical contents for the pulps that correspond to these data sets have already been presented in Tables 13 and 14. The corresponding strength properties--Concora and STFI--for handsheets made from these pulps, under selected refining criteria, are presented in Table 17. The twelve data sets were then analyzed through the RSREG module of SAS (64) and Statgraphics to get the surface and contour maps and the other multivariate second order regression analyses. The results of the analyses are provided in Tables 18 and 19 while the maps are presented Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 115 Table 16 Data Sets for Analyzing the Effects of Lignin and Pentosan Percentages on Strength Properties Name of Density Refining Pentosan Lignin Strength the pata Reqmnt. Constraint Criterion Criterion Property Set kg/m3______sec. ___ RCONSOD11 550 No % on straw % on straw Concora RCONSOD22 550 90 %onstraw %on straw Concora RCONSOD33 No 90 % on straw % on straw Concora CSOD1 550 No % on pulp % on pulp Concora CSOD2 550 90 % on pulp % on pulp Concora CSOD3 No 90 % on pulp % on pulp Concora RSTFISOD11 550 No % on straw % on straw STFI RSTFISOD22 550 90 % on straw % on straw STFI RSTFISOD33 No ' . % on straw % on straw STFI SSOD1 550 No % on pulp % on pulp STFI SS0D2 550 90 % on pulp % on pulp STFI SSOD3 No 90 % on pulp % on pulp STFI * For sodium carbonate-sodium hydroxide cooks, the nomen clature is changed substituting "COR" for "SOD", eg., RC0NS0D11 is replaced by RC0NC0R11. further throughout the discussion. At the outset, F statistics show that the second order multiple regression model works better for those data sets in which the strength properties were regressed against lignin and pentosan percent remained on straw rather than Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 116 Table 17 Strength Values of Pulps Subject to Different Constraints COOK# 550 Kg/tr? 550 Kg/m^ density or After 90 sec. density after 90 sec. of ref. of ref. Concora STPI Concora STPI Concora STFI (lb) (lb/in) (lb) (lb/in) (lb) (lb/in it 06 73.08 27.19 55.19 22.03 55.19 22.03 08 62.52 25.96 62.52 25.96 64.22 24.30 09 60.91 22.57 60. 91 22.57 74.08 26.79 11 62.97 22.99 62.97 22.99 70.36 25.30 12 61.05 22.49 61.05 22.49 75.97 26.12 * 13 68.71 25.02 40.31 17.17 40.31 17.17 15 64.21 22.86 64.21 22.86 73.22 24.64 t 16 72.49 25.37 60.85 20. 95 60.85 20.96 20 74.00 23.70 74.00 23.70 74.00 24.20 24 59.91 24.81 59.91 24.81 62.00 25.77 t 29 72.26 24.40 71.36 24.40 71.36 24.46 t 30 75.73 25.77 71.90 25.10 71.90 25.10 31 66.68 23.50 6 6 . 68 23.50 72.35 26.10 t 32 69.47 25.39 66.37 24.83 66.51 24.83 t 33 69. 60 26.70 58. 93 23.46 58.93 23.46 34 68.49 23.81 68.49 23.81 72.35 25.51 35 66.91 24.06 6 6 . 91 24.06 71.89 26.29 t 36 73.13 26.88 45.79 20.50 45. 62 20.50 38 70.79 24.54 70.79 24.54 74.86 25.85 t 3 550 kg/nr density was not achieved after 90 sec. of ref. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 117 the ones in which the strength properties were regressed against total pentosan and lignin percents on pulp. Table 18 Results of Regression of Pentosan and Lignin Contents of Pulp on Strength Properties of Handsheets (Sodium Hydroxide Cooks) Data Stationary Point Ridge/Max Regression S* Set Pent .Lig. Value of ttPent.Lig. Value o^ R2 F Prob. % % Response % % Response RCONSOD11 13. 5 9.6 62.8 17.7 5.9 82.3 .96 .03 SADDLE RCONSOD22 14. 8 6.4 62.0 17.5 4.7 96.3 .98 .01 SADDLE RCONSOD33 14. 2 4.6 73.1 17.1 4.0 87.2 .97 .01 SADDLE CSOD1 2.6 31.1 34.1 24.4 12.7 79.9 .80 .24 SADDLE CSOD2 22.1 12.7 61.7 24.4 12.5 97.7 .95 .04 SADDLE CSOD3 22.6 11.0 70.1 20.3 11.4 102 .89 .11 SADDLE RSTFISODll 17.9 -212 -48 15.9 11.3 28.4 .85 .18 SADDLE RSTFISOD22 15.8 6.8 23. 9 14.7 10.3 25.7 . 98 .01 SADDLE RSTFISOD33 15.4 2.8 26.2 15.4 3.2 26.2 .96 .02 MAX. SSOD1 24.9 11.6 24.7 21.5 16.0 25. 9 .70 .42 SADDLE SS0D2 22.4 12.6 22.5 20.2 12.9 29.0 .85 .17 SADDLE SSOD3 23.4 9.2 25. 6 20.3 10.9 34.3 .88 .12 SADDLE * Type of Response Surface Lbs. for Concora, lbs./in. for STFI Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 118 Table 19 Results of Regression of Pentosan and Lignin Contents of Pulp on Strength Properties of Handsheets (Sodium Carbonate-Sodium Hydroxide Cooks) Data Stationary Point Ridge/Max Regression S* Set Pent.Lig.Value of Pent.Lig.Value of R2 F Prob. ______% % Response % % Response______ RCONCAR11 16.5 8.1 67.6 18.1 9.3 99.1 .41 .81 SADDLE RCONCAR22 16.4 8.2 67.2 17.2 9.2 79.9 .77 .30 SADDLE RCONCAR33 15.1 8.3 73.8 16.6 9.1 76.3 .86 .16 SADDLE CCAR1 22.5 14.0 69.0 23.8 14.0 75.9 .35 .87 SADDLE CCAR2 22.5 14.1 69.7 21.8 13.7 80.4 .86 .16 SADDLE CCAR3 22.4 14.1 72.7 21.8 13.7 85.9 .95 .04 SADDLE RSTFICAR11 16.8 8.1 24.6 18.3 9.3 32.4 .92 .08 SADDLE RSTFICAR22 17.1 8.4 24.3 17.5 9.3 26.5 . 92 .07 SADDLE RSTFICAR33 -1.5 5.6 35.5 16.0 8.3 26.2 .98 .01 MAX. SCAR1 22.2 14.2 24.2 23. 6 13.4 29.6 . 61 .56 SADDLE SCAR2 22.7 14.1 24.5 21.9 13.6 25.0 .70 .41 SADDLE SCAR3 22.5 14.2 25.9 21.8 13. 6 27.1 .86 .16 SADDLE Type of Response Surface Lbs. for Concora, Lbs./in. for STPI. When correlating the Concora crush resistance to the chemical content of pulp, the optimum pentosan and lignin contents were found to be different depending on the constraints applied in the analysis. The optimum pentosan and lignin contents were higher for the non-constrained Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 119 data sets. The contour graphs of the six data sets that were generated for the Concora crush development in pure sodium hydroxide cooks revealed that: 1. In the non-constrained case both graphs, CS0D1 (Pig. 34) and RCONSOD11 (Fig. 35), illustrate a rising ridge. The Concora value increases as the pentosan percentage on pulp or the pentosan percentage remained on oven dry straw increases. At the same total pentosan con tent, the increase in total lignin percentage markedly increases the Concora value up to a certain point above which an increase in total lignin percentage has a negative effect. The reason for this may be explained as follows: Initially, pulps with higher lignin content need more refining to reach the density of 550 kg/m3, thereby strength increases. However, after a critical lignin percent is reached, the beneficial effect of higher refining level can be overshadowed by excessive fiber cutting. For instance, pulp number 16 achieves the 550 kg/m3 density in 250 seconds of refining time at 230 ml CSF but pulp number 20 comes to the same density in only 90 seconds at 310 ml CSF. 2. When the Concora value is subject to the refining constraint and the density requirement, the contour graphs of data sets RCONSOD22 (Fig. 36) and CSOD2 (Fig. 37) illus trate a saddle point within the experimental borders. The Concora value increases with increasing pentosan content Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Reproduced with permission of the copyright owner. Further reproduction prohibited w ithout permission. ithout w prohibited reproduction Further owner. copyright the of permission with Reproduced TOTAL LIGNIN X 20 iue 4 Cnor rp o CO1 aa Set. Data CSOD1 of Graph Contour 34. Figure 21 OA PNOA X PENTOSAN TOTAL 22 23 24 25 0 2 1 Reproduced with permission of the copyright owner. Further reproduction prohibited w ithout permission. ithout w prohibited reproduction Further owner. copyright the of permission with Reproduced LIGNIN OH O.K. STRAW iue 5 CnorGaho ROSD1 aa Set, Data RCONSOD11 of Graph Contour 35. Figure 5 4 17 14 15 PENTOSAN I O NO . DS . T R A W 121 Reproduced with permission of the copyright owner. Further reproduction prohibited w ithout permission. ithout w prohibited reproduction Further owner. copyright the of permission with Reproduced LI6NIN t OH O.D. STRAW iue 6 CnorGaho ROSD2 aa Set. Data RCONSOD22 of Graph Contour 36. Figure 5 6 1? 16 15 PENTOSAN 'A O NO . DS . T R A W 122 Reproduced with permission of the copyright owner. Further reproduction prohibited w ithout permission ithout w prohibited reproduction Further owner. copyright the of permission with Reproduced TOTAL LI6NIN X iue 7 CnorGaho CO2 aa Set, Data CSOD2 of Graph Contour 37. Figure \ \ T O T APE L H T O S A M 2 23 22 X 5 4555 4535 75 123 124 The higher the lignin dissolution, the greater is the Concora value. 3. When Concora values at 90 second refining level were investigated, the graphs of RCONSOD33 and CS0D3 data sets formed saddle points (Figs. 38 and 39). Concora increases with total pentosan content and pentosans remained on oven dry straw. The two data sets also show that higher lignin dissolution gives higher Concora values. However, the CSOD3 contour graph points an other maximum at the low pentosan and low lignin percentages. This is due to the higher densities that are reached with lower yield pulps. When both total pentosan and total lignin of a pulp are low, the yield should be low as well. In the same manner as for the sodium hydroxide cooks, six data sets were generated for the sodium carbonate- sodium hydroxide cooks. The results are: 1. In all data sets, Concora values increase with a rise in lignin content remained on straw, if the pentosan content remained on straw is above 16% (Figs. 40, 41 «and 42). 2. The contour graphs of total pentosan and total lignin percentage illustrate two maxima at the opposite edges of the experimental borders (Fig. 43). One of the maxima occurs at high pentosan and lignin contents whereas the other occurs at the low pentosan and low lignin contents. This probably indicates that higher pentosans Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Reproduced with permission of the copyright owner. Further reproduction prohibited w ithout permission. ithout w prohibited reproduction Further owner. copyright the of permission with Reproduced LIGNIN X ON 0.9. STRAW iue 8 Cnor rp o ROSD3 aa Set. Data RCONSOD33 of Graph Contour 38. Figure 14 15 PENTOSAN X O NO . DST . R A W 61 18 17 16 / 9-i / 125 I Reproduced with permission of the copyright owner. Further reproduction prohibited w ithout permission. ithout w prohibited reproduction Further owner. copyright the of permission with Reproduced TOTAL LI6HIH iue 9 Cnor rp o CO3 aa Set. Data CSOD3 of Graph Contour 39. Figure 26 21 T O T A LPE N T O S A N 22 23 X 24 25 126 PENTOSAN ON O.D. STRAH 14 13 14 17 Figure 4 0 . Contour Graph of RC 0 NC&R 1 1 Data Set. cjjoh veV>’,fodul 0U h e iS\o^ d V A h ’Pe' idvioe1 Reproduced with permission of the copyright o w n e r Further reproduction prohibited w ithout permission. ithout w prohibited reproduction Further r e n w o copyright the of permission with Reproduced L16N1N 2 OH O.K. STRAH 7.8 8.1 8.4 8.7 9.3 9 iue 1 CnorGaho ROCR2 aa Set. Data RCONCAR22 of Graph Contour 41. Figure 14 15 P E N T O S A1 NO !ST N0. 0 . R A H 16 17 18 19 28 128 Reproduced with permission of the copyright owner. Further reproduction prohibited w ithout permission. ithout w prohibited reproduction Further owner. copyright the of permission with Reproduced LI6HIH It OH 0.5. STRAH iue 2 CnorGah f CNA3 Dt Set. Data RCONCAR33 of Graph Contour 42. Figure 14 13 PENTOSAN 41 82819 18 17 14 V. ON O.D. STRAH 129 130 SS2 Z z CD 21 21.5 22 22.5 23 23.5 24 TOTAL PENTOSAN V. Figure 43. Contour Graph of CCAR1 Data Set. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 131 can counteract the effect of higher amounts of lignin. Again, in the case of STFI data sets generated from pure sodium hydroxide cooks, different types of response surfaces were obtained depending on the constraints. The contour graphs revealed that: 1. In the non-constrained case, STFI increases with increasing lignin content on oven dry straw and total lignin percentage on pulp. It increases also with an increase in total pentosan content (Figs. 44 and 45). 2. At 90 second refining level, the response surface illustrated by RSTFISOD33 data set shows a maximum (Fig. 46). The maximum was found at 2.8% lignin and 15.4% pentosan on oven dry straw. This is due to the higher densities obtained at lower lignin contents when the same amount of refining energy is applied to each pulp. The SAS analysis of the data set SSOD3 found the maximum ridge at 20% total pentosan and 11% total lignin content (Fig. 47). This shows that dissolution of hemicelluloses does not affect the STFI value in the experimental range when all the pulps are refined to the same level. 3. The RSTFISOD22 and SSOD2 data sets correspond to the constraints of density (550 kg/m3) and refining time (90 seconds). At low yields as well as high yields the strength development was poor because pulps could not reach the 550 kg/m3 density level at high yields within 90 seconds. Therefore, the strength development could not be Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Reproduced with permission of the copyright owner. Further reproduction prohibited w ithout permission. ithout w prohibited reproduction Further owner. copyright the of permission with Reproduced LI6NIN X ON O.O. STRAH iue 4 CnorGah f SFSD1 aa Set. Data RSTFISOD11 of Graph Contour 44. Figure 14 15 PENTOSAN X N .. STRAH ON 0.0. 16 17 18 132 Reproduced with permission of the copyright owner. Further reproduction prohibited w ithout permission. ithout w prohibited reproduction Further owner. copyright the of permission with Reproduced TOTAL LI6NIN X 28 iue 5 CnorGah f SD Dt Set. Data SSODl of Graph Contour 45. Figure 21 T O T APE L N T O S A N 22 23 X 24 25 133 Reproduced with permission of the copyright owner. Further reproduction prohibited w ithout permission. ithout w prohibited reproduction Further owner. copyright the of permission with Reproduced LIGNIN V. OH O.D. STRAH iue 6 CnorGaho RTIO3 Dt Set. Data RSTFISOD33 of Graph Contour 46. Figure 3 H 13 i I 415 14 I I 1 I I I I I n P E H T O S AXO H NO.ST D . R A H ------1 ------1 ------li 1 ------1 ------1 ------1 ------25 1 ------17 1 ------1 r i 18 ! i 1 134 Reproduced with permission of the copyright owner. Further reproduction prohibited w ithout permission. ithout w prohibited reproduction Further owner. copyright the of permission with Reproduced TOTAL II6HIN X 18 12 14 18 8 iue 7 CnorGah f SD Dt Set. Data SSOD3 of Graph Contour 47. Figure 28 21 29' TOTAL PENTOSAN PENTOSAN TOTAL 22 23 X 425 24 /21 135 136 completed. At low yields, pulps reach the required density level at comparatively low refining times. Thus, presum ably, fibrillation is not adequate. As a result, the maximum is reached at a much higher lignin content than the case of constant refining energy (Figs. 46 to 49). In sodium carbonate-sodium hydroxide cooks, contour graphs of the STFI data sets illustrated that: 1. When there is no refining constraint, STFI in creases with higher percentages of lignin remained on oven dry straw (Fig. 50). But, when total lignin and total pentosan contents are considered (Fig. 51), the STFI increases with high lignin content at low pentosan levels whereas the opposite is true for high lignin content at high pentosan contents. The last result remains an anomaly. 2. When pulps are subject to the same refining energy, the response surface is in the shape of a decreasing ridge for the pentosan and lignin content on oven dry straw (Fig. 52). STFI is higher at low pentosan on straw and remained lignin on straw contents. The same conclusion is also valid for the total pentosan and total lignin contents. Although there exists another steep edge at high pentosan and lignin content, the maximum STFI was found at the low pentosan and lignin content region, i.e., low yield region (Fig. 53). 3. As in the case of pure sodium hydroxide cooks, the Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Reproduced with permission of the copyright owner. Further reproduction prohibited w ithout permission. ithout w prohibited reproduction Further owner. copyright the of permission with Reproduced LI6NIN Y. OH O.D. STRAH iue 8 Cnor rp o RTIO2 Dt Set. Data RSTFISOD22 of Graph Contour 48. Figure 3 5 9 1 1 PENTOSAN ON O.D. STRAH 137 Reproduced with permission of the copyright owner. Further reproduction prohibited w ithout permission. ithout w prohibited reproduction Further owner. copyright the of permission with Reproduced TOTAL LI6HIN t 28 iue 9 CnorGah f SD Dt Set. Data SSOD2 of Graph Contour 49. Figure 21 T O T APE L H T O S A N 22 324 23 Y. 18 25 138 ■tprt'H' ^ ' 0 d»o^ pv° fed.vodvi'1 f a ^ eV = 0 9 ^ vfO's‘,s\°^ ,d^ce Reproduced with permission of the copyright owner. Further reproduction prohibited w ithout permission. ithout w prohibited reproduction Further owner. copyright the of permission with Reproduced total lignin X 13.4 14.2 21 iue 1 CnorGah f CR Dt Set. Data SCARl of Graph Contour 51. Figure 21.5 22 T O T APE L N T O S A N 22.5 I 323.5 23 140 Reproduced with permission of the copyright owner. Further reproduction prohibited w ithout permission. ithout w prohibited reproduction Further owner. copyright the of permission with Reproduced L16HIH X OH O.D. STRAH iue 2 CnorGah f SFCR3Dt Set. Data RSTFICAR33 of Graph Contour 52. Figure 14 13 P E N T O S ASTO2 N N0. 0 . R A H 61 18 17 16 1 ? 28 141 Reproduced with permission of the copyright owner. Further reproduction prohibited w ithout permission. ithout w prohibited reproduction Further owner. copyright the of permission with Reproduced TOTAL LI6HIH t 13.4 13.8 14.2 iue 3 Cnor rp f CR Dt Set. Data SCAR3 of Graph Contour 53. Figure 21 21.5 22 T O T APE L N T O S A N 22.5 32. 24 23.5 23 142 143 RSTFICAR22 and SCAR2 data sets have the combined con straints of the other two types of data sets. The RSTFICAR22 contour graph (Fig. 54) exhibits two edges having comparatively high STFI values at the low total lignin content, low total pentosans region and at the high total lignin content, high total pentosans region. The contour graph of SCAR2 data set (Fig. 55) indicates an optimum pentosan range of 16%-18% in which STFI increases with increasing lignin content. The Relationship Between the Optimum Cooking Variables and Optimum Pentosan and Lignin Content The RCONSOD33 data set located the maximum Concora value at 17.1% pentosan and at 4% lignin on oven dry straw. In order to find out if it were possible to reach these values in the experimental limits, Ligretl and Penretl data sets had to be investigated. When the two-variable second order polynomial equations were solved simultaneously for 4.0% remained lignin and 17.1% remained pentosan on oven dry straw, the chemical percent was found to be 7.6%, and the cooking time at 165°C was found to be 5 minutes. The 5 minutes cooking time was out of the experimental limits. The Concora crush resistance at these values was found to be 79 lbs. from the regression equation of data set T4 which is presented below: Concora=-12.98 + 24.69 Chemical - 0.10 Time -1.63 Chemical2 - 0.01 Time*Chemical + 0.001 Time2 (26) Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Reproduced with permission of the copyright owner. Further reproduction prohibited w ithout permission. ithout w prohibited reproduction Further owner. copyright the of permission with Reproduced LISHIH Y. OH O.D. STRAH 7.8 8.1 8.4 8.7 9.3 9 iue 4 CnorGaho RTIA2 Dt Set. Data RSTFICAR22 of Graph Contour 54. Figure 1514 PEHTOSAN Y. O H O . D .S T R A H 17 18 19 28 144 Reproduced with permission of the copyright owner. Further reproduction prohibited w ithout permission. ithout w prohibited reproduction Further owner. copyright the of permission with Reproduced total lignin X 13.4 13.8 14.2 21 Figure 55. Contour Graph of SCAR2 Data Set. Data SCAR2 of Graph Contour 55. Figure 21.5 22 T O T APE L N T O S A N 22.5 X 23 23.5 / l?/ 24 145 146 Even though these results seemed to contradict with the ridge analysis of the T4 data set, a look at the contour graph (Fig. 56) explained the situation. The ridge analysis located the maximum in the experimental limits around 100 minutes and 7% chemical charge and could not determine the maximum at 5 minutes cooking time because the ridge analysis investigates the response within the experimental borders. Indeed, the quadratic equation forms a saddle surface. One of the maximum edges is at 7-8% chemical charge and high cooking times, whereas the other is around the same chemical charge but at low cooking times. The first one occurs because of higher densities reached while the second one occurs due to lower carbohy drate loss. The pentosan content on oven dry straw at 7.0% chemical charge and 100 minutes cooking time was found from the Pentosan2 polynomial equation to be 14.3%. This is 2.8% lower than the 17.1% pentosan content on oven dry straw estimated for the point at 7.6% chemical charge and 5 minutes cooking time. A similar analysis was repeated with T1 and RC0NS0D11 data sets. RCONSOD11 data set located the maximum Concora at 17.7% remained pentosan and at 5.9% remained lignin content on oven dry straw. When Ligretl and Penretl polynomial equations were solved simultaneously for 5.9% lignin and 17.7% pentosan on oven dry straw, total chemical charge and cooking time were found as 6.0% and 4 minutes, Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Reproduced with permission of the copyright owner. Further reproduction prohibited w ithout permission. ithout w prohibited reproduction Further owner. copyright the of permission with Reproduced COOKING TIHE-HIN 0 iue 6 CnorGah f 4 aa Set Data T4 of Graph Contour 56. Figure 2 4 CHEMICAL '4 6 8 76 7 7 18 147 148 respectively. The Concora value at the point was found as 75 lbs. from the T1 polynomial equation (Eq. 27). Concora=91.78 - 2.53 Chemical - 0.43 Time 0.001 Chemical2 + 0.02 Time*Chemical + 0.002 Time2 (27) Ridge analysis located the maximum Concora at 4.68% total chemical and 22.45 minutes cooking time at 165°C because the experimental borders was reached at that point. However, when the contour graph of the T1 data set (Pig. 57) is extrapolated outside the experimental limits, a Concora value of 75.0 lbs. can be located at the 6.0% chemical charge and 4 minutes cooking time. The same analysis was repeated for the RCONSOD22 and T2 data sets. This is the case where both a 550 kg/m3 density requirement and a 90 second refining constraint exist. Fig. 58 depicts the contour graph of the T2 data set. Optimum chemical charge and cooking time were found as 7.0% and 2.0 minutes, respectively. The estimated Concora value from the T2 polynomial equation (Eq. 28) corresponding to the chemical charge and cooking time stated above is 77 lbs. Concora= 2.04 + 21.86 Chemical - 0.26 Time - 1.58 Chemical2 - 0.02 Chemical*Time - 0.003 Time2 (28) The value which was found by ridge analysis in the experi mental limits was 71.6 lbs at 6.56% chemical charge and 18.42 minutes cooking time. All the three data sets--Tl, T2 and T4--when Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 149 120 SB I Us l M h- CD O o 3 4 5 6 7 8 9 CHEHICAL I Figure 57. Contour Graph of T1 Data Set. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Reproduced with permission of the copyright owner. Further reproduction prohibited w ithout permission. ithout w prohibited reproduction Further owner. copyright the of permission with Reproduced COOK IH6 TIHE-HIH 100 120 54 3 iue 8 CnorGah f 2 aa Set. Data T2 of Graph Contour 58. Figure CHEMICAL 2 6 7 8 9 150 151 investigated together with Penretl and Ligretl data sets come to the same conclusion. The cooking time should be kept as low as possible depending on the constraints at the expense of small increases in total chemical charge. TALI and TAL2 data sets locate the maximum Concora around zero sodium hydroxide fraction. The optimum cooking time for TALI is less than TAL2 because the former does not have a refining constraint. Therefore, all pulps were refined till they reached 550 kg/m3 density. In the TAL2 data set, however, some of the pulps at lower cooking times could not reach the 550 kg/m3 density in 90 seconds of refining time. Hence, their strengths were lower. The distinct difference between the two data sets' contour graphs (Figs. 59 and 60) is that TALI illustrates a decreasing ridge with increasing sodium hydroxide fractions while TAL2 formes a saddle in the experimental limits. The saddle point was reached at 0.11 sodium hydroxide fraction and 24 minutes cooking time as stated by the SAS analysis. Below 24 minutes cooking time, Concora values decrease with increasing sodium hydroxide fraction. Above 24 minutes cooking time, Concora values increase with decreasing sodium hydroxide fraction. Sodium hydroxide is a more active base than sodium carbonate. Thus, at low cooking times, presence of sodium hydroxide in the cooking liquor increases delignification rate. Hence, the densities of pulps that were cooked with liquors having higher sodium Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Reproduced with permission of the copyright owner. Further reproduction prohibited w ithout permission. ithout w prohibited reproduction Further owner. copyright the of permission with Reproduced COOKING TIHE-NIH 20 38 40 0 iue 9 CnorGaho TL Dt Set. Data TALI of Graph Contour 59. Figure 00 88 01 01 0.2 0.14 0.12 8.88 0,04 0 N l OFR H A C T I O N 72! 152 Reproduced w ith permission o f the copyright owner. Further reproduction prohibited w ithout permissioh ithout w prohibited reproduction Further owner. copyright f the o permission ith w Reproduced COOKIHB TIHE-HIH 28 38 40 0 iue 0 CnorGah f A2 aa Set. Data TAL2 of Graph Contour 60. Figure 73.3 N a OFR H A C T I O N 9.12 153 154 hydroxide fractions became higher at the same refining levels. At high cooking times all pulps satisfy the 550 kg/m3 density requirement. However, as shown by the contour graph of Penret2 data set (Fig. 33), the pentosan content of pulps drops more rapidly after 33 minutes of cooking time at higher sodium hydroxide fractions. The RCONCAR22 data set located optimum pentosan content on oven dry straw subject to 90 second refining constraint at 550 kg/m3 density as 17.2%. The RCONCAR22 contour graph (Fig. 41) illustrates a pentosan range between 16 to 17.5% where Concora value increases with increasing lignin percentages. At and beyond 33 minutes cooking time, an increase in sodium hydroxide fraction caused remaining pentosan content to drop below the optimum range. The presence of an optimum pentosan range for the maximization of strength properties was in good agreement with Jayme and Lochmuller- Kerler's earlier findings as stated by Cottral (47). The TAL6 data set located the maximum at the opposite edge of the experimental borders (0.195 NaOH fraction and 24.2 minutes) (Fig. 61). The data set did not have the density requirement. Therefore, a more active chemical at intermediate cooking times increased the densities of pulps without moving the pentosan level out of the optimum range. The increasing STFI values with increasing lignin content is valid for the two cooking methods when pulps were compared at the same density. For the pure sodium Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 155 hydroxide cooks,, the optimum cooking time was longer and the optimum chemical charge was lower for the maximization of STFI than the optimum cooking time and cooking chemical found for the maximization of Concora. For sodium carbon- ate-sodium hydroxide cooks, since the total chemical charge was kept constant, optimum cooking time for STFI maximiza tion was lower as compared to the Concora. This is in good agreement with Feller's claim. Feller suggests that lignin helps load carrying ability of paper under compression (57). However, when the pulps were compared at the same refining level, STFI decreased with increasing lignin content. Hence, the TS4 and TASL6 data sets had consider ably higher optimum cooking time and chemical charge or cooking time and sodium hydroxide fractions, respectively when they were compared to other STFI data sets. The four contour graphs, TS4, TASL6 , TSl and TASL1, are presented on the following pages for comparison (Figs. 62 to 65). Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Reproduced with permission of the copyright owner. Further reproduction prohibited w ithout permission. ithout w prohibited reproduction Further owner. copyright the of permission with Reproduced COOK IH8 TIHE-HIH 28 38 48 8 0 iue 1 CnorGaho TAL of Graph Contour 61. Figure 0.08 N a OFR H A C T I O N 8.12 6 aa Set. Data 0.2 156 Reproduced with permission of the copyright owner. Further reproduction prohibited w ithout permission. ithout w prohibited reproduction Further owner. copyright the of permission with Reproduced COOK IH 6 TIHE-HIN. 4 3 iue 2 CnorGaho T4 aa Set. Data TS4 of Graph Contour 62. Figure 7 3 CHEMICAL CHEMICAL i I 8 2«.7 9 157 Reproduced with permission of the copyright owner. Further reproduction prohibited w ithout permission. ithout w prohibited reproduction Further owner. copyright the of permission with Reproduced COOKING TIHE-HIN. tea 3 iue 3 Cnor rp o T1 aa Set. Data TS1 of Graph Contour 63. Figure 4 5 CHEMICAL 6 y. 7 23.5 8 9 21.5 2-1.39 158 159 CO u T 21.5 e 0 . 0 4 0.08 0 .12 0. 16 0.2 NaOH FRACTION Figure 64. Contour Graph of TASL6 Data Set. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Reproduced with permission of the copyright owner. Further reproduction prohibited w ithout permission. ithout w prohibited reproduction Further owner. copyright the of permission with Reproduced COOK IH6 TIHE-dlH 28 18 38 48 iue 5 Cnor rp o TSl aa Set Data TASLl of Graph Contour 65. Figure i I i I i i i i I i i i I i ii .4 .8 .2 8.16 8.12 8.88 8.84 27.3 .... 'r H a OFR H A C T I O N _ 27 . ! ...... —i i i— 1— -- —1 1— ; .. - —1 —>- 1— 1— 1— ' 2« ... . 8.2 2.1.3 160 CHAPTER IX CONCLUSIONS 1. Sodium carbonate-sodium hydroxide pulping gives comparable Concora and STPI values with those obtained in soda pulping at optimum conditions. 2. Higher sodium hydroxide fraction facilitates refining. 3. The optimum sodium hydroxide fraction approaches zero when pulps are compared at the same apparent density without applying refining constraints'. 4. The optimum sodium hydroxide fraction is higher-- 0.195--when pulps are compared at the same refining energy level. 5. Data suggest that, at low cooking times, high sodium hydroxide fraction is more favorable and carbohy drate loss is less with higher sodium hydroxide fractions. At longer cooking times, high sodium hydroxide fraction deteriorates the strength properties by causing more carbohydrate dissolution. 6 . Application of high total chemical charge and low cooking time causes more lignin removal and less carbohy drate dissolution in the experimental range. 7. Concora values increase with higher pentosan 161 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 162 content remaining on oven dry straw and higher total pentosans on pulp for the soda pulps. A similar relation ship could not be found for the sodium carbonate-sodium hydroxide pulps. 8 . For the soda pulps, Concora values decrease as the lignin content remained on oven dry straw increases. A reverse relationship was found for sodium carbonate-sodium hydroxide pulps. S. When pulps are compared at the same density level, there is a positive relationship between the STFI and lignin content. When pulps are compared at the same refining energy level, there is a reverse relationship between the STFI and lignin content. t Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. CHAPTER X SUGGESTIONS FOR FURTHER STUDY This study was at the laboratory scale. Since excel lent results were obtained at this stage as regards the feasibility of a sodium carbonate-sodium hydroxide cook with a very low fraction of sodium hydroxide, the next step is to conduct this study on a pilot plant scale. A similar experimental design can be used for the pilot plant study with the exception that the cooking temperature and total chemical charge could also be put as new variables since the experiments would take less time in the pilot plant by using the continuous digester. By the same reasoning, STFI could also be optimized independently of Concora crush resistance. For a regression study with four control variables, a slightly different four dimensional experimen tal design would be necessary. Graphical representations of the results in that case would also be different. Then, two of the variables should be fixed at a constant value to see the effect from changing the other two. For example, if the temperature and total chemical charge were fixed at the optimum values, then the change of the response variable with respect to cooking time and sodium carbonate fraction could be studied. 163 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 164 The pilot plant paper machine can be used to produce paper with directionality. In that case, machine direction Concora values and cross direction STFI values should be measured. Cross direction tear resistance and machine direction tensile strength of the paper can also be included in the study, if desired, since these two proper ties are important for runnability in the converting machines. A refining study and a study concerning wet-end strength additives can be performed to increase the strength properties or to optimize the papermaking opera tions . Finally, a recycling study could also be interesting, since recycled straw paper is always present in the waste paper used in board mills in those countries in which straw constitutes one of the major fiber sources. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. LITERATURE CITED 1. Atchison, J.E., "History of paper and the importance of non-wood plant fibers, Data on non-wood plant fibers and The future of non-wood plant fibers in pulp and papermaking" In Pulp and Paper Manufacture. Third edition, editors: Kocurek, M.J., and Stevens, C.F.B., Joint Textbook Committee of the Paper Industry, 1983, vol. 1, pp. 154-174. 2. Chidester, G.H., Keller, E.L., and Sanyer, N. , "The pulping of wood", In Pulp and Paper Manufacture. Mac Donald, R.G., and Franklin, J.N. , Joint Textbook Committee of the Paper Industry, 1969, vol. 1, pp. 226-276. 3. Misra, D.K., "Secondary Fibers and Non-wood pulping", In Pulp and Paper Manufacture, Third edition, editors: Kocurek, M.J., Hamilton, F. , and Leopold, B . , Joint Textbook Committee of the Paper Industry, 1987, vol. 3, pp. 82-93. 4. Atchison, J.E., "New devolopments in non-wood plant fiber pulping--a global perspective", Wood and pulping chemistry, TAPPI PRESS, Atlanta, GA, 1989, pp. 451- 472. 5. Shouzu, H., "China's non-wood plant fibrous raw materials and their application for pulping and paper- making", International Non-Wood Fiber Pulping and Papermaking Conference Proceedings, Beijing, 1988, pp. 50-64. 6 . Rydholm, S.A., Pulping Processes. First edition, Interscience Publisher, N.Y., 1965, pp. 679-681. 7. Zhai, H., Zhongzheng, L., and Diesheng T., "Separation of fibrous cells and paranchymatous cells from wheat straw and the characteristics in soda-antraquinone pulping" International Non-Wood Fiber Pulping and Papermaking Conference Proceedings, Beijing, 1988, pp. 469-478. 165 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 166 8 . Jeyasingam, T., "Critical analysis of straw pulping methods worldwide", International Non-Wood Fiber Pulping and Papermaking Conference Proceedings, Beijing, 1988, pp. 223-232. 9. Casey, J.P., Pulp and paper: Chemistry and chemical technology. Second edition, Wiley-Interscience, N.Y., 1960, p. 402. 10. Misra, D.K., "Pulping and bleaching of non-wood fibers" In Pulp and Paper; Chemistry and Chemical Technology. Third edition, editor: Casey, J.P., Wiley-Interscience, N.Y., 1980, vol. 1, pp. 504-534. 11. Vamos, G . ,"Major rebuild for straw pulp line", Pulp and Paper International 29(3): 45 (1987). 12. Jeyasingam, T., "Industrial experience in the semi chemical pulping of straw", Tappi Non-Wood Plant Fiber Pulping Progress Report No. 17, TAPPI PRESS, Atlanta, GA, 1986, pp. 127-131. 13. Orgill, B., "Recent defibrator developments in pulping of bagasse and other non-wood fibers", Tappi Non-Wood Plant Fiber Pulping Progress Report No. 8 , TAPPI PRESS, Atlanta, GA, 1977, pp. 51-54. 14. Sutton, P., "No sulfur, no chlorine: no problem", Pulp and Paper International 29(4): 48 (1987). 15. Annus, S., and Szekeres M, , "Experiences with the reconstruction of a straw pulp mill", International Non-Wood Fiber Pulping and Papermaking Conference Proceedings, Beijing, 1988, pp. 159-169. 16. Lachenal, D., Wang, S.J., and Sarkanen, K.V., "Non sulfur pulping of wheat straw", Tappi Non-Wood Plant Fiber Pulping Progress Report No. 14, TAPPI PRESS, Atlanta, GA, 1983, pp. 71-75. 17. Zhong, X., "Straw pulping as practiced in the People's Republic of China", Tappi Non-Wood Plant Fiber Pulping Progress Report No. 14, TAPPI PRESS, Atlanta, GA, 1983, pp. 95-98. 18. Liu, M., G. , "Neutral ammonium sulfite pulping of wheat straw and the utilization of its black liquor", International Non-Wood Fiber Pulping and Papermaking Conference Proceedings, Beijing, China, July 11-14, 1988, pp. 299-304. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 167 19. Wong, A., Hull, J., and Frederick, W.J., "Potassium- based pulping of wheat straw", Tappi Pulping Confer ence Proceedings, TAPPI PRESS, Atlanta, GA, 1989, pp. 477-479. 20. Thillaimuthu, J., "The new dilute ammonia pulping process", Tappi Pulping Conference Proceedings, TAPPI PRESS, Atlanta, GA, 1984, pp. 415-426. 21. Anon, E., "New Fibers expanding its NSCMP mill in China", Pulp and Paper, 63, (7): 29 (1989). 22. Yu-Xia, Ben et a l . , "Study on mechanisms and topo- chemistries during wheat straw modified AS and NS con- tinious pulping", Wood and pulping chemistry, TAPPI PRESS, Atlanta, GA, 1989, pp. 671-677. 23. Abou-State, M.A., Ali, A.E.H., and Mostafa, N.Y.S., "Dissolving pulps from wheat straw by alkalinehydrogen peroxide pulping", Chemistry and Industry (1-8): 598 (1988). 24. Abou-State, M.A., "Highly reactive viscose pulp from wheat straw by alkaline sulphide-sulphite-antraquinone pulping", Chemistry and Industry (18): 658 (1987). 25. Kleinert, T., N. and Tayenthal, K. , "Process for decomposing vegetable fibrous material for the purpose of the simultaneous recovery both of cellulose and the incrusting ingredients", U.S. Patent No. 1,856,567 (1932). 26. Chum, H.L., Johnson, D.K., and Black, S.K., "Organo- solv pretreatment", Wood and Pulping Chemistry, TAPPI PRESS, Atlanta, GA, 1989, pp. 691-696. 27. Jiwei, C. , Dazhen, Z., and Yulin, W., "A preliminary study of organosolv pulping wheat straw with acid acetate process", International Non-Wood Fiber Pulping and Papermaking Conference Proceedings, Beijing, 1988, pp. 180-186. 28. Eroglu, A., "Soda-oxygen pulping of wheat straw", Tappi Non-Wood Plant Fiber Pulping Progress Report No. 14, TAPPI PRESS, Atlanta, GA, 1983, pp. 99-106. 29. Eroglu, A., "Soda-oxygen anthraquinone pulping of wheat straw", Tappi Non-Wood Plant Fiber Pulping Progress Report No. 17, TAPPI PRESS, Atlanta, GA, 1986, pp. 133-135. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 168 30. Upadhyaya, J.S., "Studies on alkali-oxygen- anthra- quinone delignification of bagasse", Tappi Pulping Conference Proceedings, TAPPI PRESS, Atlanta, GA, 1990, pp. 337-343. 31. Hanson, J.P., "No-sulfur pulping pushing out NSSC process at corrugating medium mills", Pulp and Paper (3): 116 (1978). 32. Patrick, K.L., "Stone container mill brings new pulp mill on-line, goes to no-sulfur", Pulp and Paper (5): 119 (1979). 33. Burns, D.T., Townshend, A., and Carter, A.H., Inorgan ic Reaction Chemistry, John Wiley & Sons, N.Y., 1981, vol. 2, pp. 94-97. 34. Gustafsson, and L. Teder, A., "Alkalinity in alkaline pulping", Svensk Papperstidning 72 (24): 795 (1969). 35. Sarkanen, K.V., and Ludwig, C.H., Lianins: Occur rence. Formation. Structure and Reactions. Wiley- Interscience, N.Y., 1971, chapter 16, pp. 639-694. 36. Sjostrom, E. , Wood chemistry: Fundamentals and ap plications . Academic Press, 1981, pp. 104-146. 37. Glasser, W.G., "Lignin" In Pulp and Paper: Chemistry and Chemical Technology. Third edition, editor: Casey, J.P., Wiley-Interscience, N.Y., 1980, vol. 1, pp. 69-78. 38. Gierer, J., Lenz, B., and Wallin, N.H., "The reactions of lignin during sulphate cooking" Acta Chem. Scand., 18, 1469 (1964). 39. Chiang, V.L., Punaoka M. , & Wang, X., "Structural changes of lignin in soda and soda-antraquinone delig nif ication of wheat straw", Tappi Non-Wood Plant Fiber Pulping Progress Report No.18, TAPPI PRESS, Atlanta, GA, 1987, pp. 51-55. 40. Bray, M.W., and Curran, E. , In Wood Chemistry, Second edition, editor: Wise, L.E. and Jahn, E.C., Reinhold Publishing Co., N.Y., 1952, pp. 982-988. 41. Bray, M.W., "Chemistry of alkaline pulp process", Paper Trade Journal 87 (23): 64 (1928). 42. Kondo, R. and Sarkanen, K.V., "Kinetics of lignin and hemicellulose dissolution during the initial stage of alkaline pulping", Holzforschung 38: 31 (1984). Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 169 43. Teder, A. and 01m, L., "Extended delignification by combination of modified kraft pulping and oxygen bleaching", Paperi Ja Puu 4a: 315 (1981). 44. Genco, J.M., Busayasakul, N., Medhora, H.K., and Robbins, W., "Hemicellulose retention during kraft pulping", Tappi 73 (4): 223 (1990). 45. Ebeling, K., "Role of fiber bonding in load-elongation properties of paper", Proceedings of National Science Foundation Workshop: Solid Mechanics Advances in Paper Related Industries, Aug. 13-15, 1986, Published by the Department of Mechanical and Aerospace Engi neering, Syracuse University, N.Y., 1990, pp. 132-143. 46. Ross, J.H., "The effect of hemicellulose content on the physical properties of pulp", Pulp and Paper Magazine of Canada 51 (1): 93 (1950). 47. Cottral, L.G., "The influence of hemicelluloses in wood-pulp fibers on their papermaking properties". Pulp and Paper Magazine of Canada 51 (9): 135 (1950). 48. Leopold, B., & McIntosh, D. , "Chemical composition and physical properties of wood fibers", Tappi 44 (3): 235 (1961). 49. McIntosh, D.C., "Tensile and bonding strengths of lobolly pine kraft fibers cooked to different yields", Tappi 46 (5): 273 (1963). 50. Spiegelberg, H.L., "The effect of hemicelluloses on the mechanical properties of individual pulp fibers", Tappi 49 (9): 388 (1966). 51. Markstrom, H., Testing Methods and Instruments for Corrugated Board. First edition, Lorentzen & Wettre. Spangbergs Tryckerier AB, Stockholm, 1988. 52. McKee, R.C., Gander, J.W., & Wachuta, J.R., "Compres sion strength formula for corrugated boxes", Paper board Pkg. 48 (8 ): 149 (1963). 53. Bernard, E., and Bouchayer, H., "Manufacturing parame ters affecting the characteristics of corrugating papers", Atip Revue 29 (4): 113 (1975). 54. Gartaganis, P.A., and Ostrowski, H.J., "Variables affecting convertibility efficiency of corrugated combined board and their measurement", Tappi, 51 (10): 471 (1968). Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 170 55. Dahm, H.P., "A comparison of neutral sulfite and cold caustic soda semichemical birch pulps for corrugating medium"/ Norsk Skogind. 16 (11): 470 (1962). 56. Fellers, C. , Handbook of Physical and Mechanical Testing of Paper and Paperboard, editor: Mark, R.E, Marcel Dekker, 1983, vol. 1, pp. 349-383. 57. Fellers, C. , Ruvo, A., Elfstrom, J., and Htun, M. , "Edgewise compression properties", Tappi 63 (6 ): 109 (1980). 58. Kulkarni, A.G., and Parkhe, P.M., "Appropriate techno logies for pulping and paper making of unconventional raw materials in India", Tappi pulping conference proceedings, TAPPI PRESS, Atlanta, GA, 1990, pp. 313- 317. 59. Misra, D.K., "Installation and operation of chemical recovery system in soda pulp mills utilising wheat- straw and bagasse as raw material", Tappi Non-Wood Plant Fiber Pulping Progress Report No. 3, TAPPI PRESS, Atlanta, GA, 1972, pp. 119-167. 60. Ibrahim, H., "Silica is no longer a problem in the recovery of heat and chemicals from nonwood plant fibers black liquor", International Non-Wood Fiber Pulping and Papermaking Conference Proceedings, Beijing, 1988, pp. 877-889. 61. Xun-Zai, N., "A study of beating wheat straw pulp with engineering plastic disc", International Non-Wood Fiber Pulping and Papermaking Conference Proceedings, Beijing, 1988, pp. 687-695. 62. Lachenal, D., Choudens C. de and Monzie P., "Cuisson de la paille de ble a 1 'oxygene en presence de carbon ate de sodium", Revue ATIP 31(4): 131 (1977). 63. TAPPI, TAPPI Test Methods. TAPPI PRESS, Atlanta, GA, 1989, vol. 1. 64. SAS Institute Inc., SAS User's Guide. Version 6 , Cary, N.C., 1990. 65. Montgomery, D.C., Design and Analysis of Experiments, Third edition, John Wiley S Sons, New York, 1991, pp. 521-568. 6 6 . Myers, R.H., Response Surface Methodology. First edition, Allyn and Bacon Inc., Boston, 1971, pp. 95. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 67. Hanson, J.P., "Semichemical pulping with NajCOj and NaOH combinations", Non-Sulfur Pulping Symposium, 1974, pp. 137-142. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. APPENDICES 172 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Appendix A Raw Data 173 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 174 Table 20 Yield Data Obtained From Sodium Hydroxide Cooks COOK # COOKING TIME (MIN.) CHEMICAL % YIELD % 3 60 6.0 56.5 5 30 8.0 51.0 6 30 4.0 66.6 7 60 6.0 57.2 8 90 4.0 61.8 9 90 8.0 54.3 10 60 6.0 57.3 11 60 6.0 56.5 12 60 8.828 51.6 13 60 3.172 69.9 14 17.58 6.0 58.2 15 102.42 6.0 55.2 16 30 4.0 64.2 17 30 8.0 54.9 18 17.58 5.5 59.0 19 17.58 7.0 56.9 20 17.58 6.5 58.4 28 17.58 6.25 58.3 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 175 Table 21 Yield Data Obtained From Sodium Carbonate-Sodium Hydroxide Cooks COOK # COOKING TIME NaOH FRACTION YIELD % (MIN.) 22 20 0.1 65.3 23 40 0.2 59.6 24 20 0.3 63.5 25 60 0.3 58.9 26 40 0.2 60.3 27 60 0.1 ' 63.0 29 20 0.1 62.2 30 20 0.0 63.9 31 34.144 0.1707 60.9 32 5.856 0.1707 61.7 33 5.856 0.0293 67.7 34 34.144 0.0293 62. 9 35 40 0.1 60.6 36 0 0.1 70.9 37 20 0.1 59.9 38 20 0.19707 62.1 39 20 0.1 61.7 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 176 Table 22 Data Obtained During the Phase I Experiments for the Optimization of Cooking Time and Chemical Charge With Respect to Concora (550 kg/m3 density requirement and 90 sec. refining constraint) RUNTOTAL COOKING TIME DENSITYREF.TIMECONCORA # CHEMICAL AT 165 C (%) (MIN.) (Kg/m3) (SEC.) (LBS.) 3 6 60 550 33 64.30 5 8 30 550 30 63.66 6 4 30 452 90 55.19 7 6 60 550 38 65.30 8 4 90 550 64 62.52 9 8 90 550 25 60.91 10 6 60 550 48 64.86 11 6 60 550 39 62.97 12 8.828 60 550 29 61.05 13 3.172 60 391 90 40.31 14 6 17.58 550 90 71.53 15 6 102.42 550 52 64.21 16 4 30 452 90 60.85 8 30 550 43 66.72 17 18 5.5 17.58 550 72 71.83 19 7.0 17.58 550 60 69.22 1 20 6.5 17.58 550 90 74.00 1 28 6.25 17.58 550 48 69.41 1 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 177 Table 23 Data Obtained During the Phase I Experiments for the Optimization of Cooking Time and Chemical % With Respect to Concora (No density requirement and 90 sec. refining constraint) I RUN TOTAL COOKING DENSITY REP.TIME CONCORA CSP j # CHEM. TIME AT (%) 165 C (Kg/m3) (S E C .) (LBS.) (ML) (MIN.) 6 60 617 90 74.23 305 1 3 5 8 30 614 90 73.63 290 4 30 452 90 55.19 445 6 7 6 60 609 90 72.86 310 8 4 90 566 90 64.22 390 » 8 90 615 90 74.08 270 10 6 60 593 90 71.40 290 11 6 60 586 90 70.36 305 12 8.828 60 610* 90 75.97* 300* 13 3.172 60 391 90 40.31 530 14 6 17.58 550 90 71.53 340 6 1 15 102.42 586 90 73.22 300 4 16 30 452 90 60.85 445 17 8 30 608 90 77.94 270 18 5.5 17.58 572 90 76.60 320 7 17.58 583 90 75.18 295 19 20 6.5 17.58 548 90 73. 69 310 1 28 6.25 17.58 590 90 77.22 290 I * values found by extrapolation Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 178 Table 24 Data Obtained During the Phase 1 Experiments for the Optimization of Cooking Time and Chemical % With Respect to Concora (550 kg/m3 density requirement and 300 ml CSF constraint) I RUN TOTAL COOKING DENSITY REF.TIME CONCORA CSF # CHEM. TIME AT <%) 165 C (Kg/m3) (S E C .) (LBS.) (ML) (MIN.) 6 60 550 33 64.30 450 I 3 8 30 550 30 63.66 450 1 5 4 30 540 185 71.25 6 300 6 60 550 38 65.30 1 7 445 4 90 550 64 62.52 1 8 450 I 8 90 550 25 60.91 440 1 9 6 60 550 48 64.86 400 10 6 60 550 39 62.97 1 11 430 12 8.828 60 550 29 61.05 430 60 550 68.71 320 13 3.172 190 1 14 6 17.58 550 90 71.53 340 6 102.42 550 52 64.21 380 15 4 30 535 190 70.72 300 1 16 8 30 550 43 66.72 410 17 18 5.5 17.58 550 72 71.83 370 19 7 17.58 550 60 69.22 360 I 20 6.5 17.58 550 90 74.00 310 I 1 28 6.25 17.58 550 48 69.41 410 1 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 179 Table 25 Data Obtained During the Phase I Experiments for the Optimization of Cooking Time and Chemical % With Respect to Concora (No density requirement, 300 ml CSF & 90 sec. refining constraints) 1 RUN TOTAL COOKING DENSITY REF.TIME CONCORA CSF 1 # CHEH. TIME AT (%) 165 C (Kg/m3) (S E C .) (LBS.) ' (ML) (MIN.) 3 6 60 617 90 74.23 305 5 8 30 608 85 72.69 300 6 4 30 452 90 55.19 445 7 6 60 609 90 72.86 310 8 4 90 566 90 64.22 390 9 8 90 608 82 72.66 300 I I 10 6 60 590 85 70. 95 300 11 6 60 586 90 70.36 305 12 8.828 60 610* 90 75.97* 3°0* 13 3.172 60 391 90 40.31 5 3 0 I 14 6 17.58 550 90 71.53 3 4 0 I 15 6 102.42 586 90 73.22 300 j 16 4 30 452 90 60.85 445 17 8 30 598 84 76.01 300 I 18 5.5 17.58 572 90 76.60 320 19 7 17.58 580 88 74.64 300 20 6.5 17.58 548 90 73.69 310 1 28 6.25 17.58 588 88 76.83 300 1 * values found by extrapolation. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 180 Table 26 Data Obtained During the Phase I Experiments for the Optimization of Cooking Time and Chemical % With Respect to Concora (550 kg/m3 density requirement and no constraints) RON TOTAL COOKING DENSITY REF.TIME CONCORA CSF I # CHEM. TIME AT (%) 165 C (Kg/m3) (SEC.) (LBS.) (ML) (MIN.) 3 6 60 550 33 64.30 450 | 5 8 30 550 30 63.66 450 j 6 4 30 550 2 60 73.08 230 7 6 60 550 38 65.30 445 8 4 90 550 64 62.52 450 I 9 8 90 550 25 60.91 440 I 10 6 60 550 48 64.86 400 11 6 60 550 39 62.97 430 12 8.828 60 550 29 61.05 430 1 13 3.172 60 550 190 68.71 3 2 0 1 14 6 17.58 550 90 71.53 3 4 0 I 15 6 102.42 550 52 64.21 3 8 0 1 16 4 30 550 250 72.49 250 1 17 8 30 550 43 66.72 410 18 5.5 17.58 550 72 71.83 370 7 17.58 550 60 69.22 19 3 6 0 1 20 6.5 17.58 550 90 74.00 310 1 28 6.25 17.58 550 48 69.41 410 1 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 181 Table 27 Data Obtained During the Phase II Experiments for the Optimization of Cooking Time and NaOH Fraction With Respect to Concora (550 kg/m3 density requirement, no constraints) RUN NaOH COOKING DENSITY REF.TIME CONCORA CSF # FRACT. TIME AT (LBS.) 165 C (Kg/m3) (SEC.) (ML) (MIN.) 22 0.1 20 550 88 72.33 370 23 0.2 40 550 61 65.38 440 24 0.3 20 550 82 59.91 380 25 0.3 60 550 43 53.71 440 26 0.2 40 550 60 65.29 430 27 0.1 60 550 90 59.08 355 29 0.1 20 550 100 72.26 340 30 0.0 20 550 110 75.73 365 31 0.1707 34.144 550 62 66.68 420 32 0.1707 5.856 550 150 69.47 300 33 0.0293 5.856 550 210* 69.60* 275* 34 0.0293 34.144 550 72 68.49 405 35 0.1 40 550 63 66.91 410 36 0.1 0 550 350* 73.13* 100* 37 0.1 20 550 82 71.38 370 38 0.19707 20 550 75 70.79 390 39 0.1 20 550 86 70.94 370 __ * values found by extrapolation Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 182 Table 28 Data Obtained During the Phase II Experiments for the Optimization of Cooking Time and NaOH Fraction With Respect to Concora (550 kg/m3 density requirement, 270 second refining constraint) I RUN NaOH COOKING TIME DENSITY REF.TIME CONCORA 1 # FRACTION AT 165 C (MIN.) (Kg/m3) (SEC.) (LBS.) 22 0.1 20 550 88 72.33 23 0.2 40 550 61 65.38 24 0.3 20 550 82 59.91 25 0.3 60 550 43 53.71 26 0.2 40 550 60 65.29 27 0.1 60 550 90 59.08 29 0.1 20 550 100 72.26 30 0.0 20 550 110 75.73 I 31 0.1707 34.144 550 62 66.68 I 32 0.1707 5.856 550 150 69.47 33 0.0293 5.856 550 210* 69.60 34 0.0293 34.144 550 72 68.49 35 0.1 40 550 63 66.91 36 0.1 0 522 270 68.49 37 0.1 20 550 82 71.38 38 0.19707 20 550 75 70.79 1 39 0.1 20 550 86 70.94 * value found by extrapolation Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 183 Table 29 Data Obtained During the Phase II Experiments for the Optimization of Cooking Time and NaOH Fraction With Respect to Concora (550 kg/m3 density requirement, 180 second refining constraint) I RUN NaOH COOKING TIME DENSITY REF.TIME CONCORA ] # FRACTION AT 165 C (MIN.) (Kg/m3) (SEC.) (LBS.) 22 0.1 20 550 88 72.33 23 0.2 40 550 61 65.38 24 0.3 20 550 82 59.91 25 0.3 60 550 43 53.71 26 0.2 40 550 60 65.29 27 0.1 60 550 90 59.08 29 0.1 20 550 100 72.26 30 0.0 20 550 110 75.73 31 0.1707 34.144 550 62 66.68 I 32 0.1707 5.856 550 150 69.47 33 0.0293 5.856 535 180* 67.41 34 0.0293 34.144 550 72 68.49 35 0.1 40 550 63 66.91 36 0.1 0 501 180 65.01 37 0.1 20 550 82 71.38 38 0.19707 20 550 75 70.79 39 0.1 20 550 86 70.94 * value found by extrapolation Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 184 Table 30 Data Obtained During the Phase II Experiments for the Optimization of Cooking Time and NaOH Fraction With Respect to Concora (550 kg/m3 density requirement, 90 second refining constraint) RUN NaOH COOKING TIME DENSITY REF.TIME CONCORA # FRACTION AT 165 C (MIN.) (Kg/m3) (SEC.) (LBS.) 22 0.1 20 550 88 72.33 23 0.2 40 550 61 65.38 24 0.3 20 550 82 59.91 25 0.3 60 550 43 53.71 26 0.2 40 550 60 65.29 27 0.1 60 550 90 59.08 29 0.1 20 544 90 71.36 I 30 0.0 20 533 90 71.90 I 31 0.1707 34.144 550 62 66.68 I 32 0.1707 5.856 527 90 66.37 I 33 0.0293 5.856 477 90 58.93 I 34 0.0293 34.144 550 72 68.49 I 35 0.1 40 550 63 66.91 1 36 0.1 0 385 90 45.79 I 37 0.1 20 550 82 71.38 I 38 0.19707 20 550 75 70.79 39 0.1 20 550 86 70.94 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 185 Table 31 Data Obtained During the Phase II Experiments for the Optimization of Cooking Time and NaOH Fraction With Respect to Concora (No 550 KO/M3 density requirement and 90 second refining constraint) RUN NaOH COOKING DENSITY REF.TIME CONCORA CSF 1 # FRACT. TIME AT 165 C (Kg/m3) (SEC.) (LBS.) (ML) (MIN.) 22 0.1 20 555 90 72.76 365 23 0.2 40 584 90 69.23 355 24 0.3 20 568 90 62.00 365 25 0.3 60 587 90 59.69 320 26 0.2 40 576 90 68.61 355 27 0.1 60 550 90 59.08 355 29 0.1 20 544 90 71.36 355 30 0.0 20 533 90 71.90 420 31 0.1707 34.144 581 90 72.35 345 32 0.1707 5.856 527 90 66.51 355 33 0.0293 5.856 477 90 58.93 420 34 0.0293 34.144 574 90 72.35 360 35 0.1 40 582 90 71.89 345 36 0.1 0 385 90 45.62 455 37 0.1 20 563 90 73.04 355 38 0.19707 20 568 90 74.86 355 39 0.1 20 558 90 72.31 360 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 186 Table 32 Data Obtained During the Phase II Experiments for the Optimization of Cooking Time and NaOH Fraction With Respect to Concora (550 kg/m3 density requirement, 300 ml CSF constraint) RUN NaOH COOKING DENSITY REF.TIME CONCORA CSF # FRACT. TIME AT 165 C (Kg/m3) (SEC.) (LBS.) (ML) (MIN.) 22 0.1 20 550 88 72.33 370 23 0.2 40 550 61 65.38 440 24 0.3 20 550 82 59.91 380 25 0.3 60 550 43 53.71 *,40 26 0.2 40 550 60 65.29 430 27 0.1 60 550 90 59.08 355 29 0.1 20 550 100 72.26 340 30 0.0 20 550 110 75.73 365 0.1707 34.144 550 62 66.68 420 31 32 0.1707 5.856 550 150 69.47 300 33 0.0293 5.856 525 165 65.95 300 34 0.0293 34.144 550 72 68.49 405 35 0.1 40 550 63 66.91 410 36 0.1 0 500 180 64.84 300 37 0.1 20 550 82 71.38 370 38 0.19707 20 550 75 70.79 390 39 0.1 20 550 86 70.94 370 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 187 Table 33 Data Obtained During the Phase II Experiments for the Optimization of Cooking Time and NaOH Fraction With Respect to Concora (No 550 kg/m3 density requirement, 300 ml CSF & 120 SEC. refining constraints) RUN NaOH COOKING DENSITY REF.TIME CONCORA CSF # FRACT. TIME AT 165 C (Kg/m3) (S E C .) (LBS.) (ML) (MIN.) 22 0.1 20 570 120 74.06 315 23 0.2 40 603 120 71.39 320 24 0.3 20 580 115 63.39 300 25 0.3 60 595 100 60.99 300 26 0.2 40 600 110 71.67 300 27 0.1 60 575 120 62.09 310 29 0.1 20 565 120 74.52 330 30 0.0 20 558 120 77.54 340 31 0.1707 34.144 588 120 73.63 310 32 0.1707 5.856 540 120 68.12 330 33 0.0293 5.856 495 120 61.56 375 34 0.0293 34.144 587 120 74.44 320 35 0.1 40 599 120 74.54 310 36 0.1 0 425 120 52.41 400 37 0.1 20 580 120 75.52 310 38 0.19707 20 583 120 78.25 325 I 1 .3.9. 0.1 20 575 120 75.22 320 8 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 188 Table 34 Data Obtained During the Phase II Experiments for the Optimization of Cooking Time and NaOH Fraction With Respect to STFI (550 kg/m3 density requirement, no constraints) RUN NaOH COOKING DENSITY REF.TIME STFI CSF # FRACT. TIME AT 165 C (Kg/m3) (SEC.) (LB/IN) (ML) (MIN.) 22 0.1 20 550 90 24.78 360 23 0.2 40 550 50 23.35 480 24 0.3 20 550 80 24.81 380 25 0.3 60 550 40 22.47 455 I 26 0.2 40 550 53 22.77 450 I 27 0.1 60 550 92 23.42 380 29 0.1 20 550 88 24.40 355 30 0.0 20 550 105 25.77 375 31 0.1707 34.144 550 58 23.50 425 32 0.1707 5.856 550 150 25.39 300 33 0.0293 5.856 550 210* 26.70* 275* 34 0.0293 34.144 550 70 23.81 415 35 0.1 40 550 57 24.06 430 36 0.1 0 550 350® 26.88* 100* 37 0.1 20 550 82 25.30 375 38 0.19707 20 550 78 24.54 390 1 39 0.1 20 550 80 25.12 385 * values found by extrapolation Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 189 Table 35 Data Obtained During the Phase II Experiments for the Optimization of Cooking Time and NaOH Fraction With Respect to STFI (550 kg/m3 density requirement/ 300 ml CSF constraint) I RUN NaOH COOKING DENSITY REF.TIME STFI CSF « FRACT. TIME AT 165 C (Kg/m3) (SEC.) (LB/IN) (ML) (MIN.) 22 0.1 20 550 90 24.78 360 23 0.2 40 550 50 23.35 480 24 0.3 20 550 80 24.81 380 25 0.3 60 550 40 22.47 455 26 0.2 40 550 53 22.77 450 27 0.1 60 550 82 23.42 380 29 0.1 20 550 88 24.40 355 30 0.0 20 550 105 25.77 375 31 0.1707 34.144 550 58 23.50 425 32 0.1707 5.856 550 150 25.39 300 33 0.0293 5.856 525 165 25.62 300 34 0.0293 34.144 550 70 23.81 415 35 0.1 40 550 57 24.06 430 360.1 0 510 180 25.42 300 37 0.1 20 550 82 25.30 375 38 0.19707 20 550 78 24.54 390 39 0.1 20 550 80 25.12 385 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. I 190 Table 36 Data Obtained During the Phase II Experiments for the Optimization of Cooking Time and NaOH Praction With Respect to STFI (550 kg/m3 density requirement, 90 sec. refining constraint) RUN NaOH COOKING DENSITY REP.TIME STPI CSP « FRACT. TIME AT 165 C (Kg/m3) (SEC.) (LB/IN) (ML) (MIN.) 22 0.1 20 550 90 24.78 360 1 23 0.2 40 550 50 23.35 480 I 24 0.3 20 550 80 24.81 380 25 0.3 60 550 40 22.47 455 26 0.2 40 550 53 22.77 '450 27 0.1 60 550 82 23.42 380 29 0.1 20 550 88 24.40 355 30 0.0 20 537 90 25.10 420 31 0.1707 34.144 550 58 23.50 425 I 32 0.1707 5.856 536 90 24.83 360 I 33 0.0293 5.856 475 90 23.46 420 34 0.0293 34.144 550 70 23.81 415 35 0.1 40 550 57 24.06 430 36 0.1 0 375 90 20.50 460 370.1 20 550 82 25.30 375 38 0.19707 20 550 78 24.54 390 I 39 0.1 20 550 80 25.12 385 | Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 191 Table 37 Data Obtained During the Phase II Experiments for the Optimization of Cooking Time and NaOH Fraction With Respect to STFI (550 kg/m3 density requirement, 180 sec. refining constraint) RUN NaOH COOKING DENSITY REF.TIME STFI CSF « FRACT. TIME AT 165 C (Kg/m3) (SEC.) (LB/IN) (ML) (MIN.) 22 0.1 20 550 90 24.78 360 23 0.2 40 550 50 23.35 480 24 0.3 20 550 80 24.81 380 25 0.3 60 550 40 22.47 455 26 0.2 40 550 53 22.77 450 27 0.1 60 550 82 23.42 380 29 0.1 20 550 88 24.40 355 30 0.0 20 550 105 25.77 375 31 0.1707 34.144 550 58 23.50 425 32 0.1707 5.856 550 150 25.39 300 33 0.0293 5.856 535 180s 26.05* 290* 34 0.0293 34.144 550 70 23.81 415 35 0.1 40 550 57 24.06 430 36 0.1 0 509 180 25.39 300 37 0.1 20 550 82 25.30 375 38 0.19707 20 550 78 24.54 390 39 0.1 20 550 80 25.12 385 * values found by extrapolation Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 192 Table 38 Data Obtained During the Phase II Experiments for the Optimization of Cooking Time and NaOH Fraction With Respect to STFI (550 kg/m3 density requirement, 270 sec. refining constraint) RUN NaOH COOKING DENSITY REF.TIME STFI CSF # FRACT. TIME AT 165 C (Kg/m3) (S E C .) (LB/IN) (ML) (MIN.) 22 0.1 20 550 90 24.78 360 23 0.2 40 550 50 23.35 480 24 0.3 20 550 80 24.81 380 $5 0.3 60 550 40 22.47 455 26 0.2 40 550 53 22.77 450 27 0.1 60 550 82 23.42 380 29 0.1 20 550 88 24.40 355 30 0.0 20 550 105 25.77 375 31 0.1707 34.144 550 58 23.50 425 32 0.1707 5.856 550 150 25.39 300 33 0.0293 5.856 550 210® 26.70* 275* 34 0.0293 34.144 550 70 23.81 415 1 35 0.1 40 550 57 24.06 430 360.1 0 519 270 25.75 190 37 0.1 20 550 82 25.30 375 38 0.19707 20 550 78 24.54 390 39 0.1 20 550 80 25.12 385 * values found by extrapolation Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 193 Table 39 Data Obtained During the Phase II Experiments for the Optimization of Cooking Time and NaOH Fraction With Respect to STFI (No 550 kg/m3 density requirement, 120 sec. refining & 300 ml CSF constraints) RUN NaOH COOKING DENSITY REF.TIME STFI CSF # FRACT. TIME AT 165 C (Kg/m3) (SEC.) (LB/IN) (ML) (MIN.) 22 0.1 20 572 120 26.10 325 23 0.2 40 612 120 26.93 320 24 0.3 20 585 115 26.58 300 25 0.3 60 615 100 25.73 300 26 0.2 40 612 110 26.37 300 27 0.1 60 592 120 25.93 315 29 0.1 20 573 120 25.17 325 30 0.0 20 560 120 26.28 350 31 0.1707 34.144 603 120 26.86 310 32 0.1707 5.856 540 120 24.99 340 33 0.0293 5.856 495 120 24.32 375 34 0.0293 34.144 593 120 26.42 320 35 0.1 40 612 120 27.01 310 36 0.1 0 420 120 22.14 400 37 0.1 20 583 120 26.93 310 38 0.19707 20 580 120 26.61 330 39 0.1 20 583 120 27.10 310 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 194 Table 40 Data Obtained During the Phase II Experiments for the Optimization of Cooking Time and NaOH Fraction With Respect to STFI (No 550 kg/m3 density requirement, 90 sec. refining .constraint) RON NaOH COOKING DENSITY REF.TIME STFI CSF FRACT. TIME AT 165 C (Kg/m3) (SEC.) (LB/IN) (ML) (MIN.) 22 0.1 20 550 90 24.78 360 23 0.2 40 595 90 25.95 355 24 0.3 20 569 90 25.77 365 25 0.3 60 610 90 25.48 320 26 0.2 40 590 90 25.09 350 27 0.1 60 559 90 23.96 355 29 0.1 20 552 90 24.46 355 30 0.0 20 537 90 25.10 420 31 0.1707 34.144 591 90 26.10 350 32 0.1707 5.856 536 90 24.83 355 33 0.0293 5.856 475 90 23.46 420 34 0.0293 34.144 578 90 25.51 360 35 0.1 40 597 90 26.29 345 36 0.1 0 375 90 20.50 455 37 0.1 20 559 90 25.74 350 38 0.19707 20 569 90 25.85 355 39 0.1 20 570 90 26.32 360 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 195 Table 41 Data Obtained During the Phase I Experiments for the Optimization of Cooking Time and Chemical % With Respect to STFI (550 kg/m3 density requiremnt, no constraints) I RUN TOTAL COOKING DENSITY REF.TIME STFI CSF * CHEM. TIME AT <%) 165 C (Kg/m3) (SEC.) (LB/IN) (ML) (MIN.) 3 6 60 550 33 23.60 450 5 8 30 550 30 23.40 450 6 4 30 550 260 27.19 230 7 6 60 550 40 23.78 440 8 4 90 550 70 25.96 430 9 8 90 550 32 22.57 420 10 6 60 550 52 23.40 385 11 6 60 550 42 22.99 415 12 8.828 60 550 28 22.49 435 13 3.172 60 550 180 25.02 325 14 6 17.58 550 85 24.50 350 15 6 102.42 550 52 22.86 390 16 4 30 550 210 25.37 270 17 8 30 550 40 22.83 420 18 5.5 17.58 550 70 23.26 385 19 7 17.58 550 55 23.43 380 20 6.5 17.58 550 82 23.70 340 28 6.25 17.58 550 45 23.93 400 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 196 Table 42 Data Obtained During the Phase I Experiments for the Optimization of Cooking Time and Chemical % With Respect to STFI (550 kg/m3 density requirement, 90 sec. refining constraint) RUN TOTAL COOKING DENSITY REF.TIME STFI CSF 1 # CHEM. TIME AT <%) 165 C (Kg/m3) (SEC.) (LB/IN) (ML) (MIN.) 3 6 60 550 33 23.60 450 5 8 30 550 30 23.40 450 6 4 30 455 90 22.03 455 7 6 60 550 40 23.78 440 8 4 90 550 70 2S.96 430 9 8 90 550 32 22.57 420 10 6 60 550 52 23.40 385 11 6 60 550 42 22.99 415 12 8.828 60 550 28 22.49 435 13 3.172 60 400 90 17.17 480 14 6 17.58 550 85 24.50 350 15 6 102.42 550 52 22.86 390 16 4 30 460 90 20.95 450 17 8 30 550 40 22.83 420 18 5.5 17.58 550 70 23.26 385 19 7 17.58 550 55 23.43 380 20 6.5 17.58 550 82 23.70 340 28 6.25 17.58 550 45 23.93 400 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 197 Table 43 Data Obtained During the Phase I Experiments for the Optimization of Cooking Time and Chemical % With Respect to STPI (550 kg/m3 density requirement, 300 ml CSF constraint) RUN TOTAL COOKING DENSITY REF.TIME STFI CSF # CHEM. TIME AT (%) 165 C (Kg/m3) (SEC.) (LB/IN) (ML) (MIN.) 3 6 60 550 33 23.60 450 5 8 30 550 30 23.40 450 6 4 30 540 185 26.64 300 7 6 60 550 40 23.78 440 8 4 90 550 70 25.96 430 9 8 90 550 32 22.57 420 10 6 60 550 52 23.40 385 11 6 60 550 42 22.99 415 12 8.828 60 550 28 22.49 435 13 3.172 60 550 180 25.02 325 14 6 17.58 550 85 24.50 350 15 6 102.42 550 52 22.86 390 16 4 30 540 190 24.88 300 17 8 30 550 40 22.83 420 18 5.5 17.58 550 70 23.26 385 19 7 17.58 550 55 23.43 390 20 6.5 17.58 550 82 23.70 340 28 6.25 17.58 550 45 23.93 400 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 198 Table 44 Data Obtained During the Phase I Experiments for the Optimization of Cooking Time and Chemical % With Respect to STFI (550 kg/m9 density requirement,90 sec. refining constraint) RUN TOTAL COOKING DENSITY REF.TIME STFI CSF # CHEM. TIME AT (%) 165 C (Kg/m3) (S E C .) (LB/IN) (ML) (MIN.) 3 6 60 614 90 27.05 305 5 8 30 612 90 27.86 290 6 4 30 455 90 22.03 455 7 6 60 612 90 25.89 310 8 4 90 574 90 24.30 390 9 8 90 615 90 26.79 270 10 6 60 585 90 25.42 290 11 6 60 588 90 25.30 305 12 8.828 60 623 90 26.12 320 13 3.172 60 400 90 17.17 540 14 6 17.58 556 90 24.84 340 15 6 102.42 586 90 24.64 300 16 4 30 460 90 20.96 450 17 8 30 609 90 25.85 270 18 5.5 17.58 581 90 24.64 320 19 7 17.58 599 90 25.87 295 20 6.5 17.58 564 90 24.20 310 28 6.25 17.58 591 90 26.09 ?.?fl.. 1 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 199 Table 45 Data Obtained During the Phase I Experiments for the Optimization of Cooking Time and Chemical % With Respect to STFI (No 550 kg/m3 density requirement, 90 sec. refining & 300 ml CSF constraints) RUN TOTAL COOKING DENSITY REF.TIME STFI CSF « CHEM. TIME AT (%) 165 C (Kg/m3) (SEC.) (LB/IN) (ML) (MIN.) 3 6 60 614 90 27.05 305 5 8 30 608 85 27.58 300 6 4 30 455 90 22.03 455 7 6 60 612 90 25.89 310 8 4 90 574 90 24.30 390 9 8 90 608 82 26.34 300 10 6 60 582 85 25.25 300 11 6 60 588 90 25.30 305 12 8.828 60 623 90 26.12 320 13 3.172 60 400 90 17.17 540 14 6 17.58 556 90 24.84 340 15 6 102.42 586 90 24.64 300 16 4 30 460 90 20.96 450 17 8 30 603 88 25.54 300 18 5.5 17.58 581 90 24.64 320 19 7 17.58 595 86 25.67 300 20 6.5 17.58 564 90 24.20 310 28 6.25 17.58 588 88 25.93 300 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Appendix B Regression Equations and Summary of Statistical Analyses for Data Sets That Correlate Chemical Compositions of Pulps to the Cooking Variables 200 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 201 Pure Sodiuro Hydroxide Cooka KAPPA1 DATA SET KAPPA NUMBER IS REGRESSED AGAINST CHEMICAL % AND COOKING TIME AT 165°C. Predicted second order regression equation is: Kappa = 105.9284 - 5.0581 CHE + 0.4588 TIME - 0.4069 CHE1 - 0.0257 (TIMExCHE) - 0.0015 TIME2 LIGRET1 DATA SET LIGNIN % ON STRAW IS REGRESSED AGAINST CHEMICAL % AND COOKING TIME AT 165°C. Predicted second order regression equation is: Lignin = 16.3084 - 2.1527 CHE + 0.0282 TIME + 0.0693 CHE2 - 0.0015 (TIMExCHE) - 0.0000945 TIME2 PENTRET1 DATA SET PENTOSAN % ON OD STRAW IS REGRESSED AGAINST CHEMICAL % AND COOKING TIME AT 165°C. Predicted second order regression equation is: Pentosan = 31.9981 - 3.8141 CHE - 0.1586 TIME + 0.2520 CHE2 + 0.0079 (TIMExCHE) + 0.0007 TIME2 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 202 TLP1 DATA SET TOTAL LIGNIN % IN MIXED PULP IS REGRESSED AGAINST CHEMICAL % AND COOKING TIME AT 165°C. Predicted second order regression equation is: Total Lignin % = 16.7510 - 0.6670 CHE + 0.0574 TIME - 0.0430 CHE2 - 0.0033 (TIMExCHE) - 0.0002 TIME2 TPP1 DATA SET TOTAL PENTOSAN % IN MIXED PULP IS REGRESSED AGAINST CHEMICAL % AND COOKING TIME AT 165°C. Predicted second order regression equation is: Total Pentosan % = 30.0964 - 1.8855 CHE - 0.1392 TIME + 0.1779 CHE2 + 0.0048 (TIMExCHE) + 0.0008 TIME2 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 203 Sodium Carbonate-Sodiuro Hydroxide Cooks KAPPA2 DATA SET KAPPA NUMBER IS REGRESSED AGAINST NaOH FRACTION AND COOKING TIME AT 165°C. Predicted second order regression equation is: Kappa = 81.4935 + 2.8829 F + 0.0796 TIME - 18.8809 F2 - 0.4500 (TIMExF) - 0.0012 TIME2 LIGRET2 DATA SET * LIGNIN % ON OD STRAW IS REGRESSED AGAINST NaOH FRACTION AND COOKING TIME AT 165°C. Predicted second order regression equation is: Kappa = 9.2950 - 2.4478 F - 0.0617 TIME + 8.2760 F2 - 0.0798 (TIMExF) + 0.0012 TIME2 PENRET2 DATA SET PENTOSAN % ON OD STRAW IS REGRESSED AGAINST NaOH FRACTION AND COOKING TIME AT 165°C. Predicted second order regression equation is: Pentosan = 19.4358 + 5.9995 F - 0.1813 TIME - 7.0625 F2 - 0.1965 (TIMExF) + 0.0003 TIME2 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 204 TLP2 DATA SET TOTAL LIGNIN % IN MIXED PULP IS REGRESSED AGAINST NaOH FRACTION AND COOKING TIME AT 165°C. Predicted second order regression equation is: Total Lignin % = 13.7234 + 0.1179 F + 0.0139 TIME - 2.9702 F2 - 0.0500 (TIMExF) + 0.0000176 TIME2 TTP2 DATA SET TOTAL PENTOSAN % IN MIXED PULP IS REGRESSED AGAINST NaOH FRACTION AND COOKING TIME AT 165°C. Predicted second order regression equation is: Total Pentosan % = 23.2436 + 7.6199 F - 0.04S8 TIME - 28.4050 P2 + 0.0525 (TIMExF) + 0.0002 TIME2 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 205 Table 46 Pure Sodium Hydroxide Data Sets' Regression Results (Chemical Properties vs Cooking Time & Total Chemical %) DATA SET STATIONARY PT. RIDGE/MAX REGRESSION TYPE OP CHE% TIME IRESP CHE% TIME RESP R2 F PROB SURFACE Kappal -15.6 296 213 3.3 70.9 104 0.99 0.01 MAXIMUM Ligretl 15.8 22.8 -0.4 3.2 64.0 11.3 0.99 0.01 SADDLE Penretl 6.4 75.4 13.8 3.7 35.6 17.7 0.91 0.09 MINIMUM TLP1 -21.3 351 34.0 3.3 70.8 16.5 0.99 0.01 MAXIMUM TPP1 4.2 78.2 20.7 8.8 53.3 24.3 0.88 0.13 MINIMUM Table 47 Sodium Carbonate - Sodium Hydroxide Data Sets' Regression Results (Chemical Properties vs Cooking Time & HaOH Fraction) DATA SET STATIONARY PT. RIDGE/MAX REGRESSION TYPE OP FRAC.TIME RESP PRAC.TIME RESP R2 P PROB. SURFACE Kappa2 0.15 5.9 81.5 0.05 35.4 85.0 0.43 0.70 SADDLE Ligret2 0.32 35.7 7.8 0.15 0. 0 9.1 0.77 0.30 MINIMUM Penret2 -0.04 33.1 16.3 0.17 0 .2 20 .2 0.90 0.10 SADDLE TLP2 0.28 -31.0 13.5 0.04 33.3 14.1 0.45 0.68 SADDLE TPP2 0.22 90.3 21.9 0.14 0. 0 23. 8 0.56 0.63 SADDLE Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Appendix C ANOVA Tables and Regression Equations for Concora-STFI Linear Regression 206 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 207 Table 48 Regression Analysis for the Linear Model: Concora=a+bSTFI Dependent Variable : STFI.TS1 Independent Variable : Concora.Tl Parameter Estimate Standard Error T Value Prob. Level Intercept 11.9649 4.0839 2.92978 0.00981 Slope 0.1794 0.0608 2.95203 0.00937 Analysis of Variance Source Sum of Squares Df Mean Square F-Ratio Prob. Model 10.1836 1 10.1837 8.7145 0.009 Residual 18.6975 16 1.1686 Total 28.8811 17 Correlation Coefficient 0.5938 R2 0.3526 Table 49 Regression Analysis for the Linear Model: Concora=a+bSTFI Dependent Variable : STFI.TS2 Independent Variable : Concora.T2 Parameter Estimate Standard Error T Value Prob. Level Intercept 10.9047 2.2985 4.7442 0.00022 Slope 0.1885 0.3578 5.26835 0.00008 Analysis of Variance Source Sum of Squares Df Mean Square F-Ratio Prob. Model 33.9113 1 33.9112 27.7554 0.00008 Residual 19.5486 16 1.2218 Total 53.4598 17 Correlation Coefficient 0.7964 R2 0.6343 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 208 Table SO Regression Analysis for the Linear Model: Concora=a+bSTFI Dependent Variable : STFI.TS4 Independent Variable : Concora.T4 Parameter Estimate Standard Error T Value Prob. Level Intercept 7.9680 1.9919 4.00016 0.00103 Slope 0.2396 0.0282 8.48425 0.00000 Analysis of Variance Source Sum of Squares Df Mean Square P-Ratio Prob. Model 87.5866 1 10.1837 8.7145 0.009 Residual 19.4684 16 1.1686 Total 107.0550 17 Correlation Coefficient 0.9045 R2 0.8181 Table 51 Regression Analysis for the Linear Model: Concora=a+bSTFI Dependent Variable : STFI.TAS1 Independent Variable : Concora.TAl Parameter Estimate Standard Error T Value Prob. Level Intercept 14.4244 2.8521 5.05743 0.00014 Slope 0.1493 0.0420 3.55623 0.00287 Analysis of Variance Source Sum of Squares Df Mean Square F-Ratio Prob. Model 11.6067 1 11.6067 12.6468 0.00287 Residual 13.7664 15 0.9178 Total 25.3732 16 Correlation Coefficient 0.6763 R2 0.4574 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 209 Table 52 Regression Analysis for the Linear Model: Concora=a+bSTFI Dependent Variable : STFI.TAS2 Independent Variable : Concora.TA2 Parameter Estimate Standard Error T Value Prob. Level Intercept 14.8755 1.5333 9.70149 0.00000 Slope 0.1387 0.0234 5.91783 0.00003 Analysis of Variance Source Sum of Squares Df Mean Square F-Ratio Prob. Model 16.6749 1 16.6748 35.0207 0.00003 Residual 7.1421 15 0.4761 Total 23.8170 16 Correlation Coefficient 0.: >7 0.7001A ' Table 53 Regression Analysis for the Linear Model: Concora=a+bSTFI Dependent Variable : STFI.TAS6 Independent Variable : Concora.TA6 Parameter Estimate Standard Error T Value Prob. Level Intercept 15.0269 1.8659 8.05365 0.00000 Slope 0.0276 5.38421 0.000080.1485 Analysis of Variance Source Sum of Squares Df Mean Square F-Ratio Prob. Model 21.0624 1 21.0624 28.9898 0.00008 Residual 10.8982 15 0.7265 Total 31.9606 16 Correlation Coefficient 0.8118 R2 0.6590 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Appendix D Sample Calculations 210 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 211 Sample Calculations Cook # 35 PuIp 1. Calculation of yield: Yield % = [Total pulp weight x (1 - moisture fraction)] x 100 / (oven dry straw fed to the digester) = [423.4 g x (1 - 0.7483)] x 100 / 176 g = 60.6 % 2. Calculation of pentosan %: pentosan % = (mg. xylan) / 10 x o.d. pulp = 163 / 10 x 0.7089 = 23.0 % Handsheet 1. Surface area of Concora strips = 1.93548 E-3 m2 (Concora cutter, 6 by 1/2 in strip) conversion factor = 20,341 kg pt/m3 g 2. Surface area of STFI strips = 2.66699 E-3 m2 (15 mm. TM1 precision cutter, 7 in by 15 mm. strip) conversion factor = 14,762 kg pt/m3 g 3. Calculation of density: strip #1 of handsheets prepared from 90 second refined pulp for Concora: Density=[(weight of strip g)/(caliper pts.)] x conv. factor = (0.266/9.40) x 20,341 = 575.6 kg/m3 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Appendix E General Information on Straw 212 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 213 Table 54 Characteristics of Non-Wood Fibrous Materials Compared to Pulpwood <10, p. 518) Fiber a Cellu Fenlo- Raw Average Average Ash Ltgnln lose ssns Material Croup length (mm) dlam tttr (fr) 1. Straws anti trasses 1.1- 1.5 9-13 6-8 17-19 33-38 27-32 Open Rlea straw O.S 8.5 14-20 12-14 28-36 23-25 Open 2. Stalks and reeds 1.0- l.S 8-20 3-6 18-22 33-43 28-32 Open Sugarcane bagasse depithed 1.7 20 2 19-21 40-43 30-32 Open 3. Woody stalks with bast fibers: woody stems 0 .2 - 0.3 10-11 2-3 23-27 31-33 15-22 Dense bast fibers 20.0-25.0 16-22 1-2 1-6 60+ 2-6 Open 4. Leaf fibers 6.0-9.0 16-18 1 7-10 53-64 17-24 Open 5. Bamboo 3.0-4.0 14 1-3 22-30 50+ 16-21 Dense For Comparison Temperate coniferous woods 2.7-4.6 32-43 1 26-30 40-45 10-13 Dense Temperate hardwoods 0.7-1.6 • 20-40 1 18-25 38-49 19-23 Dense Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 214 Table 55 Fiber Dimensions of Non-Wood Plant Fiber Pulps (1, p. 164) Average Average length, diameter Non-wood plant fibers mm microns Abaca (Manila hemp) 6.0 24 Bagasse (depithed) 1.0-1.5 20 Bamboo 2.7-4 15 Com stalks & sorghum (depithed) 1.0-1.5 20 Cotton fiber 25 20 Cotton stalks 0.6-0.8 20-30 Crotalaria (sunn hemp) 3.7 25 Esparto 1.5 12 Flax straw 30. 20 Hemp 20. 22 Jute 2.5 20 Kenaf bast fiber , 2.6 20 Kenaf core material 0.6 30 . Rags ' 25. 20 Reeds 1.0-1.8 10-20 Rice straw 0.5-1.0 8-10 Sisal 3.0 20 Wheat straw 1.5 15 Wood fibers Temperate zone coniferous wood 2.7-4.S 32-43 Temperate zone hardwoods 0.7-1.S 20-40 Mixed tropical hardwoods 0.7-3.0 20-40 Eucalyptus 0.7-1.3 20-30 Gmelina 0.8-1.3 25-35 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 215 Table 56 Preeness Values of Cooked Non-Wood Pulps in Comparison to Wood Pulps3 (10, p. 523) Unbleached Bleached Bagasse 20 - 22 Bamboo 14-16 16-18 Esparto 16 18 Reeds 18-19 22 Rice straw 40-42 42-45 Wheat straw 30 35 For comparison purposes Softwood pulp 12 15-16 Hardwood pulp 15-16 18-19 JFreeness in ®SR Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 216 Table 57 Chemical Properties of Non-Wood Plant Fibers (1, p. 165) Cross and Bevan Alpha cellulose cellulose Ugnln Pentosans Ash Silica • Type of fiber % % % % % % Stalk libers — straw — rice 43-49 28-36 12-16 2328 15-20 9 - 1 4 — wheat 49-54 29-35 16-21 26-32 4.39 3-7 — barley 47-48 31-34 14-15 24-29 3 7 3-6 — oat 44-53 31-37 16-19 27-33 6-6 4-6.5 — rye 50-54 33-35 16-19 27-30 2-5 0.5-4 — cane — sugar 49-62. 32-44 19-24 27-32 1.35 0.7-3.5 — bamboos 57-66 26-43 21-31 15-25 1.7-4.8 0.69 — grasses — esoarto 50-54 33-38 17-19 27-32 6-8 — saoai 54.5 22.0 . 23.9 6.0 — reeds — phragmites - 57.0 44.75 22.8 20.0 2.9 2.0 communis Bast libers — seed flax tow 75.9-79.2 45.1-68.5 10.1-14.5 6.0-17.4 2.34.7 — seed flax 47 34 23 25 5 — kenaf 47-57 31-39 14.5-18.7 22-22.7 1.7-5.0 — jute(1) 57-53 21-26 18-21 0.5-1.8 Leaf libers — abaca (Manila) 78 60.8 8.8 17.3 1.1 — sisal (agave) 55-73 43-56 7.6-9.2 21.324 0.31.1 Seed hull — cotton linters 80-65 0.8-1.8 libers Woods — coniferous 53-62 40-45 26-34 7-14 <1 — deciduous 54-61 38-49 23-30 19-26 <1 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 217 o 1.5 3.0 2.2 2.3 2.9 8.7 16.5 3 (10 4.1 1.4 0.9 4.9 0.6 5.1 17.0 15.7 13.4 38.0 40.5 34.4 70.9 70.3 74.6 27.072.1 27.1 75.0 75.5 Soils Soils H Light ' ' 1.2 (%) 3.7 2.4 2.4 2.4 1.2 2.8 1.2 4.2‘ 4.4 53.7 52.334.6 54.0 55.8 11.2 26.2 74.0 Soils Summer Wheat Heavy Straw 2.3 1.3 1.6 l.S 1.5 1.6 0.4 0.7 7.4 69.038.0 69.9 39.8 26.4 70.2 Soils Light Oats 1.3 1.8 2.4 3.2 1.3 1.2 1.5 2.3 1.2 11.9 69.4 39.4 71.7 26.0 Soils Heavy Table 58 1.1 1.7 1.9 2.3 1.2 12.3 14.9 14.8 12.0 36.7 36.4 35.4 39.5 Barley Winter 1.4 3.2 3.2 2.0 1.5 2.6 1.8 2.5 2.9 2.5 2.3 3.3 3.5 2.5 3.5 16.2 16.9 15.5 16.7 16.3 36.0 12.0 53.4 54.4 55.0 54.2 10.5 8.7 71.3 71.0 27.0 26.4 '73.9 72.8 Barley Summer Average Composition of European ofholocellulose) % Pure Pentosan Pentosan in Ash in Pure Ash in (as Remainder Lignin Ilolocellulose Alpha cellulose 39.4 Pentosan Insoluble ash 2.7 Ether extract Insoluble protein 1.4 1.4 Total protein Water extract Total ash lission of the copyright owner. Further reproduction prohibited without permission. S c l C o Q. —■5 O CD -o 218 o . ONO O CM O «- I?** »— (M r- T < 2- . o o ^ co a> ai o cm o *r ga* oi oi r- CM CM CM CM cq m; a> 0 3©' « o n m 01 ^ = V) co rj in CM f** N N r» if) 1 8 5 oo l O C O C O vn U3 h- O C» m © co co o © m c> cm co in a 5*5 a? CO s cm co lO h* t- CO if CM CO CO ~ 03 (O h* o *- O WJ* ai ai ai co ibstO’fi6 id cb cb cb I - « re c: a : 0) Q 3 O ur O C V co IA V) o c in IB (B o *n <* £ > £ w m o 5 oc J5 Z uj UJ Reproduced with permission of fhe copyright owner. Further reproduction prohMed without permission. 219 Table 60 Pulping Processes for Non-Wood Plant Fibrous Materials (1, p, 166) Yield of pulp, % Raw materials Pulping process Typo of pulp Unbleached Bleac Mixed cereal straw Lime Paoer 55-65 Ume Strawboard 7o-ao Soda or kraft Paper 55 50 Soda or kraft Corrugating 67 Rice straw Soda Paper 42 39 Esparto Soda Paper 45-55 42-52 Sabai Soda Paper Reeds (Phragmites communis) NSSC Paoer 52.7 43-50 Soda Paper 45.7-50.7 42-48 Sulfate Paper 45.3-50.7 42-43 Neutral sulfite . Corrugating 62 Papyrus Soda Paper 38-35 27 Bagasse (depithed) Soda or sulfate Multiwall sack paper 60 ... Bleached paper 50-52 45-48 Corrugating • 70 Unerboard 63 Bamboo Soda Paoer 44-45 40-41 Sulfite Paper 46-47 42-43 Seed flax, tow Soda Cigarette paper 42-45 40 Textile flax tow Soda Paper 65 Jute Soda . Paoer 62 58 Kenaf Soda or sulfate Paper 45-51 40-46 Abaca (Manila) Soda or sulfate Paper 45-54 43-52 Sisal (agave) Soda Paper 69 60 Cotton linters Soda or kraft Paper 70 Dissolving 65 Cotton rags Ume soda Paper 70 Soda Paper 70 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 220 Table 61 Pulping Conditions for Batch Pulping of Straw (3, p. 8 8 ) Neutral Lfmo Urn e-Soda Soda Sulfite Sulfite Chemical (% on CaO 6-12 5-10 CaO NaOH 6-15 NaOH 10-12 10 NajSOj or moisture-free straw) or + + Na,S 2-3 Na,SOj + 2-5 MgO 12-18 3-4 NajCOj NaOH Liquor-lo-straw ratio after steaming 4:1 5:1 4:1-7:1 4:1-6:1 3:1-7:1 Time, h 6-10 6-8 2.5-4 2.5-4 2-4 Temperature. °C 125-140 120-140 150-170 150-170 160-170 Variety of pulp Coarse Coarse High-yield semi High-yield setni- High-yield semi produced chemical and chemical and chemical and bleachable bleachable bleachable grade grade grade Yield (crude yield). % from: Wheat + rye straws 70-85 . 70-80 48-70 50-70 53-65 Rice straw 70-80 65-70 40-45 42-47 45-48 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 221 Table 62 Cooking Conditions Using Different Raw Materials in a Rapid Pulping Cycle in a Pandia Continuous Pulping System (10, p. 513) Chemical Pulping Applied Dwell Steam Pulp Perman Chemical as N s ]0 • Time Pressure Yield ganate Raw Material Process (%) (min) (kPa) (psi) (55) No. Wheat straw* Soda 4.6 8 515 75 67 — Soda 10.0 8 550 80 50 - Rice straw* Soda 9.8 5.5 690 100 39 4.9 Sugarcane bagasse* Sulfate 12.0 10 895 130 52 7.5 Reeds* Soda 12.8 20 855 130 48 15.0 , Esparto Soda 12.4 20 ’ 825 120 52 6.0 Napier grass* Soda 15.0 30 1035 150 44 15.0 Bamboo (Bambusa arundinacea) Sulfate 18.2 30 855 130 45 10.0 Reeds* Neutral- 19.1 25 1035 150 53 1-2.3 Sulfite Neutral- 10.7 10 1035 150 62 24.4 Sulfite *Uncieaned raw fiber. "Depithed or cleaned. ^Cleaned reeds: chemical applied as Na, SO,. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 2 2 2 Official Methods of Analysis of the Association Of Official Agricultural Chemists Editorial Board WillianrHorwitz, Chairman and Editor Ninth Edition, 1960 Published by the Association Of Official Agricultural Chemists P.O. Bos 540, Benjamin Franklin Station Washington 4, D.C. Indirect Method for Determination of Acid Insoluble Lignin 6.904 Indirect Method (32)-First Action P P . 91-92 Ext. 1 b sample with alcohol-benzene (1 + 2 ) 4 Repeat washing twice and then wash residue hr in Soxhlct or comparable app. (extn vessel may into flask by forcing 7-8 ml 5% H:SO. downward be either coarse porosity Alundum or paper thru filter stick, using air pressure. Wash stick thimble, closed at top with filter paper or plus further with the H;SO„ finally adding enough tin of cotton). Wash sample in thjmbJs with suction, bring total vol. to ca 150 ml. Reflux vigorously on using 2 small portions alcohol followed by 2 small hot plate 1 hr, adding H ;0 occasionally to main portions ether. Heat at 45* in non-sparking oven; tain original voL Filter off acid. Wash residue wi: h to drive off ether, and transfer sample to 25b mil three 20-30 ml portions hot Hjf>. two 15-20 ml wide-mouth erlenmcver. Add 40 ml 1%w in » / portions alcohol, and two 15 ml portions ether. peptin in OJ.Y HCi, wetting sample well by adding! Leave vac. on few min. to dry residue, and trans small portion of the soln, stirring or shaking fer from stick to flask by tapping and brushing. thoroly, and finally washing down sides of flasks Heat to drive off any residual ether. If disk formed with remainder of soln. Incubate at 40* overnight; upon drying is difficult to break up into finely Add 20-30 ml hot H -0 and filter, using filter divided state (sometimes in case of immature stick. (Filter sticks are made with Pvrcx fritted plant samples), disperse residue in ether in flask glass disk, 30 mm diam., medium porosity. Thin and then boil off ether on steam bath. Add 20 ml layer of pre-ashed diatomaceous earth (Hvflo 72% HiSOi at 20* to residue and hold 2 hr at 20*. Supercel, or similar filter-aidl is sucked onto disk stirring occasionally. Add 125 ml HjO, filter, wash from H :0 suspension. This is usually sufficient fur ouec with 20 ml hot H;0, and filter again. Wash easy filtration; if not, add extra Supercel to ma residue from filter stick and reflux as before 2 hr, terial being filtered. Some sticks filter slowly with1 using 150 ml 3% H.-SO,. Filter residue onto gooch some samples. It is advisable to obtain more than! with asltestoa pad and wash with hot H :0 until needed and discard slow-filtering ones. It is con free of acid. Dry at 105-110* and det. lignin by venient to arrange filter sticks in set of 12 at loss in wt on ignition at 600*. tached to vac. manifold by mbl>er tubing.) Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. BIBLIOGRAPHY Abou-State, M.A. (1987). Highly reactive viscose pulp from wheat straw by alkaline sulphide-sulphite- anthraquinone pulping. Chemistry and Industry, 18, 658. Abou-State, M.A., Ali, A.E.H., SMostafa, N.Y.S. (1988). Dissolving pulps from wheat straw by alkaline hydro gen peroxide pulping. Chemistry and Industry. 8_, 598. Annus, S., & Szekeres M. (1988). Experiences with the reconstruction of a straw pulp mill. International Non-Wood Fiber Pulping and Papermaking Conference Proceedings (pp. 159-169). Atlanta, GA: Tappi Press. Anon, E. (1989). New fibers expanding its NSCMP mill in China. Pulp and Paper. 63.(7), 29. Aronovsky, S.I., & Lathrop, E.C. (1949). 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Non-sulfur pulping process for corrugating medium using sodium carbonate and sodium hydroxide. Abstract, U.S. Patent No. 3,954,553, Official Gazette of the United States Patent and Trademark Office (December 11. 1990). 1121(2), 228. Ebeling, K., (1990). Role of fiber bonding in load- elongation properties of paper. Proceedings of National Science Foundation Workshop: Solid mechanics advances in paper related industries (pp. 132-143). Syracuse, NY: Syracuse University Press. Effland, M.J. (1977). Modified procedure to determine acid-insoluble lignin in wood and pulp. Tappi, 60(10), 143. Ernst, A.J., Clark, T.F., & Wolff, I.A. (1960). Corrugating pulp from wheat straw by cold soda process. Tappi, .43.(2.), 34. Eroglu, A. (1983). Soda-oxygen pulping of wheat straw. Tappi Non-Wood Plant Fiber Pulping Progress Report No. 14 (pp. 99-106). Atlanta, GA: Tappi Press. Eroglu, A. (1986). Soda-oxygen anthraquinone pulping of wheat straw. 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Semi-chemical straw pulp process for the manufacture of fibre raw materials for fluting liner, wrapping paper and solid cardboard. International Non-wood Fiber Pulping and Papermaking Conference Proceedings (pp. 206-215). Atlanta, Ga: Tappi Press. Gustafsson, L., & Teder, A. (1969). Alkalinity in alkaline pulping. Svensk Papperstidning, 72.(24), 795. Hammond, J.A., & Karter, E.M. (1977, January 14). High yield semichemical wood pulping process. Abstract, U.S. Patent No. 4,073678, Official Gazette of the United States Patent and Trademark Office (December 11. 19901 . 1121(2) . 162. Hanson, J.P. (1974). Semichemical pulping with NajCOj and NaOH combinations. Non-sulfur pulping symposium (pp. 137-142). Atlanta, GA: Tappi Press. Hanson, J.P. (1978). No-sulfur pulping pushing out NSSC process at corrugating medium mills. Pulp and Paper, 5(3), 116. Hurter, A.M. (1988). Utilization of annual plants and agricultural residues for the production of pulp and paper. Tappi Pulping Conference Proceedings, (pp. 139-160). Atlanta, Ga: Tappi Press. Ibrahim, H. (1988). Silica is no longer a problem in the recovery of heat and chemicals from nonwood plant fibers black liquor. International Non-Wood Fiber Pulping and Papermaking Conference Proceedings (pp. 877-889). Atlanta, GA: Tappi Press. Jeyasingam, T. (1986). Industrial experience in the semichemical pulping of straw. Tappi Non-Wood Plant Fiber Pulping Progress Report No. 17 (pp. 127-131). Atlanta, GA: Tappi Press. Jeyasingam, T. (1988). Critical analysis of straw pulping methods worldwide. International Non-Wood Fiber Pulping and Papermaking Conference Proceedings (pp. 223-232). Atlanta, GA: Tappi Press. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 227 Jiwei, C. , Dazhen, Z., & Yulia, W. (1988). A preliminary study of organosolv pulping wheat straw with acid acetate process. International Non-Wood Fiber Pulping and Papermaking Conference Proceedings (pp. 180-186). Atlanta. GA: Tappi Press. Judt, M. (1988). The science of non-wood fibre pulp and papermaking. International Non-Wood F*iber Pulping and Papermaking Conference Proceedings (pp. 8-23). Atlanta, GA: Tappi Press. Kleinert, T.N. (1966). Mechanism of alkaline delignification. Tappi. 4.9(2), 53. Kleinert, T.N., & Tayenthal, K. (1932). Process for decomposing vegetable fibrous material for the purpose of the simultaneous recovery both of cellulose and the incrusting ingredients. U.S. Patent No. 1,856.567. Kleppe, P.J. (1970). Kraft pulping. Tappi. 53.(1), 35. Kondo, R., & Sarkanen, K.V. (1984). Kinetics of lignin and hemicellulose dissolution during the initial stage of alkaline pulping. Hoizforschung, 38, 31. Kulkarni, A.G., Mathur, R.M., & Panda, M. (1989). Nature of spent liquors from pulping of non-woody fibrous raw materials. Wood and Pulping Chemistry. (pp. 485-492). Atlanta, GA: Tappi Press. Lachenal, D., Choudens C., & Monzie P. (1977). Cuisson de la paille de ble a l'oxygene en presence de carbonate de sodium. Revue ATIP. 3JL(4), 131. Lachenal, D., Wang, S.J., & Sarkanen, K.V. (1983). Non sulfur pulping of wheat straw. Tappi Non-Wood Plant Fiber Pulping Progress Report No. 14 (pp. 71-75). Atlanta, GA: Tappi Press. Lemon, S., & Teder, A. (1973). Kinetics of the delignification in kraft pulping. Svensk Papperstidning. 76.(11), 407. Leopold, B., & McIntosh, D. (1961). Chemical composition and physical properties of wood fibers. Tappi. 44(3), 235. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 228 Liang, W.Z., Zhou, F.C., Xiao, X.R., & Wang, Z.H. (1988). Organosolv pulping characteristics of wheat straw. International Non-Wood Fiber Pulping and Papermaking Conference Proceedings (pp. 271-280). Atlanta, GA: Tappi Press. Liu, H.G. (1988). Neutral ammonium sulfite pulping of wheat straw and the utilization of its black liquor. International non-wood fiber pulping and papermaking conference (pp. 299-304). Atlanta, GA: Tappi Press. Markstrom, H. (1988). Testing methods and instruments for corrugated board. Stockholm, Sweden: Spangbergs Tryckerier AB. Matthews, H.C. (1974). Carbohydrate losses at high temperature in Kraft pulping. Svensk Papperstidning. 17.(9), 629. McIntosh, D.C. (1963). Tensile and bonding strengths of lobolly pine Kraft fibers cooked to different yields. Tappi . .46(5), 27 3. McKee, R.C., Gander, J.W., SWachuta, J.R, (1963). Compression strength formula for corrugated boxes. Paperboard Pkg.. 48(8), 149. Misra, D.K. (1971). Modern methods of collecting, purchasing, storing and preservation of straw. Tappi Non-Wood Plant Fiber Pulping Progress Report No. 2 (pp. 161-175). Atlanta, GA: Tappi Press. Misra, D.K. (1972). Installation and operation of chemical recovery system in soda pulp mills utilizing wheat-straw and bagasse as raw material. Tappi Non- Wood Plant Fiber Pulping Progress Report No. 3 (pp. 119-167). Atlanta, GA: Tappi Press. Misra, D.K. (1975). Industrial experiences and problems involved in stock preparation and papermaking utilizing non-wood fibrous materials. Tappi Non-Wood Plant Fiber Pulping Progress Report No. 6 (pp. 7-22). Atlanta, GA: Tappi Press. Misra, D.K. (1980). Pulp and paper: Chemistry and chemical technology (3rd ed., vol. 1, pp. 504-534). New York, NY: Wiley Interscience. Misra, D.K., (1987). Cereal straw. Pulp and paper manufacture (vol. 3, pp. 82-93). Atlanta, GA: Tappi Press. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 229 Mohan, R., Prasad, R., Yadav, R., Ray, A.K., & Rao, N.J. (1988). Pulping studies of wheat straw using soda and soda-anthraquinone processes. International Non- Wood Fiber Pulping and Papermaking Conference Proceedings (pp. 339-349). Atlanta, GA: Tappi Press. Montgomery, D.C. (1991). Design and analysis of experiments (3rd ed.). New York: John Wiley & Sons. Myers, R.H. (1971). Response surface methodology. (p. 95). Boston, MA: Allyn & Bacon Inc.. Orgill, B. (1977). Recent defibrator developments in pulping of bagasse and other non-wood fibers. Tappi Non-Wood Plant Fiber Pulping Progress Report No. 8 (pp. 51-54). Atlanta, GA: Tappi Press. Patrick, K.L. (1979). Stone container mill brings new pulp mill on-line, goes to no-sulfur. Pulp and Paper. 5., 119. Peterson, P.B. (1989). Industrial application of straw. Wood and Pulping Chemistry (pp. 179-183). Atlanta, GA: Tappi Press. Ross, J.H. (1950). The effect of hemicel1ulose content on the physical properties of pulp. Pulp and Paper Magazine of Canada. 5.1(1), 93. Rydholm, S.A. (1965). Pulping processes. (pp. 679-681). New York, NY: Wiley Interscience. Sarkanen, K.V. (1971). Lignins: Occurrence, formation, structure and reactions (pp. 639-694). New York, NY: Wiley Interscience. SAS Institute. (1990). SAS user's guide, version 6 . Cary, NC: SAS Institute. Shouzu, H. (1988). China's non-wood plant fibrous raw materials and it's application for pulping and papermaking. International Non-Wood Fiber Pulping and Papermaking Conference Proceedings (pp. 50-64). Atlanta, GA: Tappi Press. Sjostrom, E. (1981). Wood chemistry: Fundamentals and applications (pp. 104-146). New York, NY: Academic Press. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 230 Spiegelberg, H.L. (1966). The effect of hemicelluloses on the mechanical properties of individual pulp fibers. Tappi. 49(9), 388. Sutton, P. (1987, April). No sulfur, no chlorine: No problem. Pulp & Paper International, 29.(4), 48. Tappi. (1989). Tappi test methods (vol. 1). Atlanta, GA, Tappi Press. Teder, A., & Olm, L. (1981). Extended delignification by combination of modified kraft pulping and oxygen bleaching. Paperi Ja Puu 4a. 315. Thillaimutu, J. (1984). The new dilute ammonia pulping process. Tappi pulping conference proceedings (pp. 415-426). Atlanta, GA: Tappi Press. Upadhyaya, J.S. (1990). Studies on alkali-oxygen- anthraquinone delignification of bagasse. Tappi pulping conference proceedings (pp. 337-343). Atlanta, Ga: Tappi Press. Vamos, G. (1987). Major rebuild for straw pulp line. Pulp and Paper International . .29.(3), 45. Vroom, K.E. (1957). The "H" factor: A means of expressing cooking times and temperatures as a single variable. Pulp and Paper Magazine of Canada, .58.(3), 228. Wong, A., Hull, J., & Frederick, W.J. (1989). Potassium- based pulping of wheat straw. Tappi Pulping Con ference Proceedings (pp. 477-479). Atlanta, Ga: Tappi Press. Xiao-an, L ., Zhong-zheng, L ., & Die-sheng, T. (1988). Studies on dissolving procedure in alkaline solution of wheat straw. International Non-Wood Fiber Pulping and Papermaking Conference Proceedings (pp. 305-317). Atlanta, GA: Tappi Press. Xun-Zai, N. (1988). A study of beating wheat straw pulp with engineering plastic disc. International Non- Wood Fiber Pulping and Papermaking Conference Proceedings (pp. 687-695). Atlanta, GA: Tappi Press. Yu-Xia, B. (1989). Study on mechanisms and topochem- istries during wheat straw modified AS and NS continuous pulping. Wood and pulping chemistry (pp. 671-677). Atlanta, GA: Tappi Press. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. V u 18 a as U • o u u o «=>a> h « • 44 •H 4-1 w W 4-> O 04 m 18 0> L Li o u >4 as (8 £ a> >4 II i xp CO rH o c 44 M 44 m xP xp m ■8* Xf p~ CO CN P- <3\ <3S xp -CO r- CN CO c- O H o o o a o a) Li co CN o CO o r~ co r- o CO o in o CM Li 18 O • • • • • ‘H CN CO E pH o CO CO XP o CO o P- m xp CO CN CO rH p* O CO o o o o