AN ABSTRACT OF THE THESIS OF
Daniel D. Euhus for the degree of Honors Baccalaureate of Science in Chemical
Engineering presented on May 14, 1999. Title: Effects of Caustic Addition on Black
Liquor Rheology and Thermal Characteristics.
Abstract approved: _____________________________________________________
Willie E. (Skip) Rochefort, Ph.D.
Abstract
An important by-product of the kraft pulping process, black liquor is currently
used in most pulp mills to produce steam in a recovery boiler. Two important black
liquor characteristics are viscosity and burning (firing) characteristics, which determine
the operating efficiency of the recovery boiler. Kraft black liquor is a complicated
material, with physical properties varying greatly depending on starting material (chip
supply), pulping process (chemicals), solids content and temperature. The effects of
solids content and temperature on black liquor and black liquor viscosity have been
extensively studied. However, considerably less work has been done to examine the
effect of caustic addition on black liquor viscosity and firing characteristics.
In the present study, the effective alkali content (EAr) of the black liquor was
variedby a controlled addition of caustic (NaOH) solution. Several mill samples of
varying history and % solids were studied using a rheometer to measure viscosity and
thermal characterization (DSC and TGA) to determine burning characteristics. The
results indicate that the addition of caustic to black liquor significantly reduces viscosity
at all solids contents and temperatures up to a maximum EAr level of approximately 4%
where the viscosity then either levels off or starts to increase depending on the type of
black liquor. The results show that caustic addition does not adversely effect burning
characteristics as determined by the energy required to evaporate the sample water prior
to combustion and the subsequent thermal degradation point of the organic matter.
The results of the present studies support the use of caustic addition to control
black liquor viscosity in the evaporator and recovery boiler processes. The "optimum"
EAr level to obtain the lowest viscosity must be determined for the specific process
liquor.
Copyright by Daniel D. Euhus
May 14, 1999
All Rights Reserved
Effects of Caustic Addition on Black Liquor Rheology and Thermal Characteristics
by
Daniel D. Euhus
A PROJECT
submitted to
Oregon State University
University Honors College
in partial fulfillment of
the requirements for the
degree of
Honors Bachelor of Science in Chemical Engineering (Honors Associate)
Presented May 14, 1999
Commencement June 1999
Honors Bachelor of Science in Chemical Engineering project of Daniel D. Euhus
presented on May 14, 1999
APPROVED:
Mentor, representing Chemical Engineering
Committee Member, representing Forest Products
Committee Member, representing the Institute of Paper Science and Technology
Interim Chair, Department of Chemical Engineering
Dean of the University Honors College
I understand that my project will become part of the permanent collection of Oregon State
University, University Honors College. My signature below authorizes release of my
project to any reader upon request.
Daniel D. Euhus
I would like to acknowledge Dr. Skip Rochefort and Dr. Jim Frederick for considerable
assistance by providing laboratory space and guidance during the course of my research.
I would also like to acknowledge the three corporations that provided samples for my
thesis work:
 Pope and Talbot
 Willamette Industries
 Weyerhaeuser
Table of Contents
I.
Introduction
1
II.
Procedures and Methodology
2
Theory of Rheology
Relevance of Rheology to this Study
Application of Rheology to this Study
Differential Scanning Calorimetry Theory
Relevance of DSC to this Study
Application of DSC to this Study
Thermogravimetric Analysis Theory
Relevance of TGA to this Study
Application of TGA to this Study
Liquor Preparation and Analysis
Sample Repeatability and Error Analysis
Rheological Repeatability and Error
DSC Repeatability and Error
TGA Repeatability and Error
III.
Results
15
Rheological Results
Differential Scanning Calorimetry Results
Thermogravimetric Analysis Results
IV.
2
4
4
5
6
6
7
7
8
8
9
10
12
14
Conclusions and Discussion
Rheological Conclusions
Differential Scanning Calorimetry Conclusions
Thermogravimetric Analysis Conclusions
Final Conclusions
15
19
21
23
23
24
25
25
Bibliography
26
Appendices
27
Table of Appendices
Appendices
27
Appendix A: Rheology, Mill A Experimental Data
28
Appendix B: Rheology, Mill B Experimental Data
30
Appendix C: Rheology, Mill C Experimental Data
32
Appendix D: Rheology, Rheometrics Error Calculation
36
Appendix E: Rheology, Bohlein Error Calculation
37
Appendix F: Differential Scanning Calorimetry
39
Appendix G: Thermogravimetric Analysis
44
Table of Figures
Figure
1.
Couette Geometry for Rheometry
3
2.
Mill A, 66% solids First and Second Run Repeatability at 100ºC
11
3.
Mill A, 66% solids Second Run Repeatability at 100ºC
11
4.
Mill C, 71.5%, 6.0% EAr, Reproducible and Non-Reproducible DSC
13
5.
Mill C, 71.5%, 6.0% EAr, Reproducibility of TGA
14
6.
Mill A, 49% Black Liquor Viscosity at Various EAr at 27ºC.
15
7.
Mill B, 41% Black Liquor Viscosity at Various EAr at 27ºC.
16
8.
Mill C, 71.5% Black Liquor Viscosity at Various EAr at 100ºC
17
9.
Mill C, 71.5% Black Liquor Viscosity at Various EAr at 115ºC
18
10.
Mill C, 71.5% Temperature Comparisons (100ºC and 115ºC)
18
11.
Mill C, 71.5%, 3.5% EAr Black Liquor DSC
19
12.
Mill C 71.5% DSC Comparisons
20
13.
Mill C 71.5% TGA Curve
21
14.
Mill C 71.5% TGA Comparisons
22
Appendices Figures and Tables
Table (T) or Figure (F)
T A1.
F A1.
T A2.
F A2.
First Run Mill A Black Liquor Viscosity Data (cP)
First Run Mill A Viscosity Graph
Second Run Mill A Black Liquor Viscosity Data (cP)
Second Run Mill A Viscosity Graph
28
28
29
29
T B1.
F B1.
T B2.
F B2.
First Run Mill B Black Liquor Viscosity Data (cP)
First Run Mill B Viscosity Graph
Second Run Mill B Black Liquor Viscosity Data (cP)
Second Run Mill B Viscosity Graph
30
30
31
31
T C1.
F C1.
T C2.
F C2.
T C3.
F C3.
T C4.
F C4.
First Run Mill B Black Liquor Viscosity Data (cP)
First Run Mill B Viscosity Graph
Second Run Mill B Black Liquor Viscosity Data (cP)
Second Run Mill B Viscosity Graph
First Run Mill C Black Liquor Viscosity Data, 100ºC
First Run Mill C Viscosity Graph, 100ºC
Second Run Mill C Black Liquor Viscosity Data, 100ºC
Second Run Mill C Viscosity Graph, 100ºC
32
32
33
33
34
34
35
35
T D1. Rheometrics Experimental Error Data and Calculations
36
T E1. Bohlein Experimental Error Data
T E2. First Run Experimental Error Calculations
T E3. Second Run Experimental Error Calculations
37
37
38
F F1.
F F2.
F F3.
F F4.
F F5.
F F6.
F F7.
Mill C 3.5% Black Liquor DSC (N2 Purge)
Mill C 4.0% Black Liquor DSC (N2 Purge)
Mill C 4.5% Black Liquor DSC (N2 Purge)
Mill C 5.0% Black Liquor DSC (N2 Purge)
Mill C 6.0% Black Liquor DSC (N2 Purge)
Mill C 3.5% Black Liquor DSC (Air Purge)
Mill C 3.5% Black Liquor DSC Comparison
39
39
40
40
41
42
42
F G1.
F G2.
F G3.
F G4.
F G5.
Mill C 3.5% Black Liquor TGA (N2 Purge)
Mill C 4.0% Black Liquor TGA (N2 Purge)
Mill C 4.5% Black Liquor TGA (N2 Purge)
Mill C 5.0% Black Liquor TGA (N2 Purge)
Mill C 6.0% Black Liquor TGA (N2 Purge)
44
44
45
45
46
This thesis is dedicated to my loving wife who encouraged me through many late hours in
the lab and on the computer. Without her encouragement, I would have given up!
I love you Kimberly!