Allen J Smith Dis

235 Pages·2011·3.22 MB·English

Hot Water Extraction and Subsequent Kraft Pulping of Pine Wood Chips

by

Allen J. Smith

A dissertation submitted to the Graduate Faculty of
Auburn University
in partial fulfillment of the
requirements for the Degree of
Doctor of Philosophy

Auburn, Alabama
May 9, 2011

Keywords: prehydrolysis, biorefinery, pulp,
hemicellulose, sugar,

Copyright 2011 by Allen Joseph Smith

Approved by

Gopal Krishnagopalan, Chair, Professor Emeritus of Chemical Engineering
Harry Cullinan, Director of Alabama Center for Paper and Bioresource Engineering
Steve Duke, Associate Professor of Chemical Engineering
Oladiran Fasina, Associate Professor of Biosystems Engineering
Abstract
This research investigated the effects of pre-extraction time, temperature, and pH
on the rate and quantity of sugars recovered from Loblolly pine wood chips and the
impact this treatment has on pulp kappa number and yield. Composition analysis of raw
chips, extracted chips, pulp, and hydrolyzate were performed to assess the hemicellulose
extraction efficiency and subsequent loss during kraft pulping of Loblolly pine. A
pseudo kinetic model of prehydrolysis extraction was developed from the hydrolyzate
sugar concentration data.
Preliminary experiments demonstrated the potential for influencing pulp
properties and sugar recovery in hydrolyzate through on-line control of prehydrolysis pH,
reaction temperature, and time. A second set of experiments examined these factors and
added a presoak period to the design matrix. A third set of experiments used a best case
of pre-extraction conditions to test five potential pulping additives.
It was concluded that the extraction rate for all sugars was increased with either
increasing temperature from 140 to 170°C or decreasing pH from 4.5 to 3.0. The
hydrolysis was selective for hemicellulose as opposed to cellulose by using temperature
at 140°C. Both pH and temperature also impacted the degradation rate of sugars in
solution. The 24 hour presoak at 25°C with various pH levels had no measurable effect
on hydrolysis rate or pulp yield.
ii
The additives tested in this research: anthraquinone, acetaldehyde, ethanolamine,
lithium aluminium hydride, and hydroxylamine, were not successful in recovering pulp
yield from extracted chips to that of a standard kraft cook with the conditions tested.
More work could be justified with hydroxylamine or to test the use of anthraquinone in
conjunction with hydroxylamine or another successful additive.
A pseudokinetic model of the extraction was calculated using an activation energy
of 27 kcal/mole for hemicellulose hydrolysis and a term for the acid concentration. This
modified H-factor model described the sugar extraction data except when significant
degradation of sugars was observed. The data for chip weight loss and pulp yield also fit
a smooth curve when plotted against the modified H-factor.

iii
Acknowledgments
Dr. Gopal has been not just my academic advisor but also a friend from the time
of my undergraduate experience at Auburn University from 1985-89 through my
professional experience in the pulp and paper industry. I have not always heeded his
advice, but I typically have seen its wisdom in hindsight.
Dr. Harry Cullinan was particularly helpful in the latter stages of this project as I
was exploring different potential forms for the model. The work seemed to get more and
more complex each week until he reminded me of Occam’s razor.
I had many valuable discussions with Dr. Sung Hoon Yoon in the time that we
were both working in Wilmore 156. Some of them involved prehydrolysis experiments.
Dr. Duke and Dr. Fasina both provided valuable comments about the dissertation
proposal and this document.
Funding for this project was provided by the Auburn University Natural
Resources Management and Development Institute and the Masada Resource Group,
LLC through the Alabama Center for Paper and Bioresource Engineering.
The Rock –Tenn Company supplied the pine chips.
Dr. Y. Y. Lee’s group at Auburn University assisted with the carbohydrate
composition analysis. In particular, Rajesh Gupta and Kang Li trained this investigator in
preparation of samples for analysis on the HPLC and in reading the chromatograms.
iv
Dr. Saeed Maghsoodloo assisted with interpretation of statistical data and basic
instruction in the use of the Minitab statistical software program.
Many people have encouraged me during this process and I will not attempt to
name all that have kept me going. In particular Martha Evans has expressed confidence
in me for the 30 years that I have known her as a teacher and friend. She has been
particularly diligent in this over the past five years. Jim Killian and Bill Josephson have
had exactly the right words at times when I felt that I would not have the will to finish.
Janine and Elizabeth were children when I started this project and are now
beautiful young women. They have reversed roles and been an example to me of getting
their homework done and performing well in school.
Tony and Mary Ruth Smith have been just who parents should be for a child
working through graduate studies even if that child has children of his own. Thanks
Mom for refocusing me when I got distracted. Dad, your insightful and irreplaceable
comments on this document completely reshaped the tone into what it should be.
Penny has stood beside me, in front of me, behind me… all the time showing me
that she loves me just for who I am even though she doesn’t always agree with what I do.
I hope that my love in return is as apparent.
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Table of Contents
Abstract ............................................................................................................................... ii
Acknowledgments.............................................................................................................. iv
List of Tables ...................................................................................................................... x
List of Figures .................................................................................................................... xi
List of Abbreviations ..................................................................................................... xviii
Chapter 1 Introduction ....................................................................................................... 1
1.1 Research Synopsis .................................................................................................... 1
1.2 Perspective ................................................................................................................ 2
1.3 Dissertation Organization ......................................................................................... 4
1.4 Biorefineries .............................................................................................................. 5
1.5 Biomass Feedstock ................................................................................................. 10
1.6 Pulping Methods ..................................................................................................... 18
Chapter 2 Review of Previous Work ............................................................................... 28
2.1 Dissolving Pulp ....................................................................................................... 28
2.2 Alcohol Production from Wood Hydrolysis ........................................................... 34
2.3 Value Prior to Pulping ............................................................................................ 36
Chapter 3 Experimental Apparatus and Procedures ........................................................ 41
3.1 Materials and Equipment ........................................................................................ 41
3.2 Experimental Procedures ........................................................................................ 46
vi
3.3 Analytical Procedures ............................................................................................. 50
Chapter 4 Prehydrolysis of Pine Wood Chips ................................................................. 51
4.1 Preliminary Work ................................................................................................... 51
4.2 Second Preliminary Work ....................................................................................... 53
4.3 pH Controlled Prehydrolysis of Pine Wood Chips ................................................. 55
4.4 Material Balances ................................................................................................... 61
4.5 Prehydrolysis Conclusions ...................................................................................... 66
Chapter 5 Prehydrolysis Designed Study ........................................................................ 67
5.1 Designed Experiment Factors ................................................................................. 68
5.1.1 Variation of Prehydrolysis Time ...................................................................... 68
5.1.2 Variation of Temperature ................................................................................. 68
5.1.3 Variation of pH ................................................................................................ 69
5.1.4 Variation of Presoak Conditions ...................................................................... 70
5.2 Hydrolysis Target ................................................................................................... 71
5.3 Experimental Design ............................................................................................... 72
5.4 Results ..................................................................................................................... 77
5.4.1 Prehydrolyzate Composition ............................................................................ 77
5.4.2 Chip Weight Loss ............................................................................................ 94
5.4.3 Pulp Yield ........................................................................................................ 96
5.4.4 Additional Cooks ........................................................................................... 101
Chapter 6 Pulp Yield Recovery ..................................................................................... 108
6.1 Anthraquinone ...................................................................................................... 111
6.2 Acetaldehyde ........................................................................................................ 117
vii
6.3 Ethanolamine ........................................................................................................ 120
6.4 Lithium Aluminium Hydride ................................................................................ 125
6.5 Hydroxylamine ..................................................................................................... 128
6.6 General Yield Improvement Conclusions ............................................................. 140
Chapter 7 Value Prior to Pulping Model ....................................................................... 141
7.1 Historical Development ........................................................................................ 143
7.1.1 Wood hydrolysis or prehydrolysis models .................................................... 143
7.1.2Kraft pulping models ...................................................................................... 147
7.2 Model Development ............................................................................................. 150
7.2.1 The Modified H-factor ................................................................................... 150
7.2.2 Validation ....................................................................................................... 168
7.2.3 Additional Improvements Required ............................................................... 169
Chapter 8 Conclusions and Suggestions for Future Research ....................................... 170
8.1 Conclusions from this Research ........................................................................... 170
8.1.1 Prehydrolysis Experiments ............................................................................ 172
8.1.2 Yield Improvement ........................................................................................ 173
8.1.3 Modeling Results ........................................................................................... 173
8.2 Suggestions for Further Investigation ................................................................... 174
8.2.1 Prehydrolysis Variables ................................................................................. 174
8.2.2 Additional Yield Improvement Research ...................................................... 176
8.2.3 Model Enhancement ...................................................................................... 178
8.2.4 Improvements to Testing or Experimental Procedures .................................. 181
8.3 Final Comments .................................................................................................... 182
viii
Bibliography ................................................................................................................... 184
Appendix 1 Minitab 15 Statistical Results..................................................................... 193
Appendix 2 Non-Standard Test Methods ...................................................................... 195
A2.1 ABC Liquor test ................................................................................................. 195
A2.2 Black Liquor Residual Alkali Test .................................................................... 196
Appendix 3 Cook Worksheets and Calculations ........................................................... 197

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List of Tables
Table 1 Loblolly pine wood composition measurements. ............................................... 42
Table 2 Macromolecule composition estimation matrix. ................................................ 43
Table 3 Preliminary study, selected conditions and results. ............................................ 53
Table 4 Latin square experimental plan. .......................................................................... 67
Table 5 Latin square conditions for prehydrolysis screening. ......................................... 73
Table 6 Latin square experiment order and labeling. ...................................................... 74
Table 7 Conditions and results for additional prehydrolysis cooks. .............................. 102
Table 8 Treatment conditions and results for ethanolamine treatment. ......................... 123
Table 9 Hydroxylamine treatment conditions and results. ............................................ 136
Table 10 Hydrolysis activation energy values from literature. ...................................... 147

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