INTERFACIAL PROPERTIES AND PHASE EQUILIBRIA FOR MIXTURES
RELEVANT IN THE OIL AND GAS INDUSTRY
Vorgelegt von
Oscar Gabriel Nino-Amezquita, M. Sc.
aus Bogotá (Kolumbien)
von der Fakultät III
Prozesswissenschaften
der Technischen Universitat Berlin
zur Erlangung des akademischen Grades
Doktor der Ingenieurwissenschaften
Dr.-Ing.
genehmigte Dissertation
Promotionsausschuss:
Vorsitzender: Prof. Dr.-Ing. habil. Günter Wozny
Gutachterin: Prof. Dr. rer. nat. habil. Sabine Enders
Gutachter: Prof. Dr.-Ing. Rudolf Eggers
Tag der wissenschaftlichen Aussprache: 24.02.2014
Berlin 2014
D83
ACKNOWLEDGMENTS
It would not have been possible to write this doctoral thesis without the help and
support of the kind people around me, to only some of whom it is possible to give
particular mention here. This work would have never been completed without the
advising and support of Prof. Sabine Enders, who was always willing to help and
worked together with me during all this time. During my time working with her it was
possible for me to grow not only academically but also as a person. Furthermore I
would like to thank all colleagues and co-workers at the Chair of Thermodynamics at
the TU-Berlin. The permanent discussions and a nice working environment made my
work of this Thesis a pleasant task. In particular I would like to thank all my former
office companions, Tim Zeiner, Udo Dorn and Karin Daniel, with whom I shared a lot
of time and many interesting academical and non-academical dialogues. My
gratitude also goes to the Department of thermal separation processes, heat and
mass transfer of the TU Hamburg-Harburg, led by Prof. Rudolf Eggers, for the
support and the valuable experimental data that allowed validating various parts of
this work. Also Prof. Günter Wozny is to be thanked for taking the time to take part of
the proofing Comission. Twister B.V. is also to be thanked for the interesting
discussions and financial support. Last but not least, I want to specially thank the
DFG for the financial support (En291/6-1) during this work.
TABLE OF CONTENTS
1. INTRODUCTION ................................................................................................. 1
2. PHASE EQUILIBRIA OF LOW-MOLECULAR WEIGHT SYSTEMS ................... 4
2.1. Thermodynamic Framework .......................................................................... 4
2.2. Calculations of Phase Equilibria .................................................................... 6
Molecular Based EOS ......................................................................................... 9
The SAFT EOS and its modifications ................................................................ 11
3. THE INTERFACIAL TENSION .......................................................................... 21
3.1. Generalities ................................................................................................. 21
3.2. Measurement of the interfacial tension ........................................................ 21
3.3. The Density Gradient Theory ...................................................................... 24
The DGT for pure substances ........................................................................... 24
The DGT for mixtures ........................................................................................ 28
4. APPLICATION OF THE DENSITY GRADIENT THEORY FOR PURE
COMPONENTS ........................................................................................................ 32
4.1. Non-polar Substances ................................................................................. 32
4.2. Polar Substances ........................................................................................ 36
Simple Polar Components ................................................................................. 36
Polar Components Exhibiting Self-Association .................................................. 39
4.3. Substances containing Sulphur ................................................................... 42
5. APPLICATION OF THE DENSITY GRADIENT THEORY FOR MIXTURES ..... 48
5.1. Binary Mixtures ............................................................................................ 48
Non-polar Mixtures ............................................................................................ 48
Mixtures of a polar and a non-polar component ................................................ 58
Water Mixtures .................................................................................................. 67
5.2. Ternary Mixtures.......................................................................................... 89
6. CONCLUSIONS AND OUTLOOK ..................................................................... 93
7. REFERENCES .................................................................................................. 96
ii
LIST OF TABLES
Table 1: Free monomer fractions defined for each association scheme ................... 13
Table 2: Universal constants for the PC-SAFT EOS . .............................................. 17
Table 3: Influence parameter
for non-polar components using PC-SAFT. ........... 32
Table 4: Comparison of parameters for water with the models 2B and 4C. .............. 39
Table 5: Parameter set for the description of the properties of SO3 ......................... 44
Table 6: Comparison of parameter sets for the description of the properties of SO2 45
Table 7: Comparison of parameter sets for the description of the properties of H2S 47
Table 8: Calculated binary interaction parameters for PC-SAFT .............................. 52
Table 9: Calculated binary interaction parameters for SAFT-VR .............................. 52
iii
LIST OF FIGURES
Figure 1: Graphic description of Maxwell’s criterion. .................................................. 6
Figure 2: Comparison between experimental and calculated interfacial tensions for
n-alkanes. ................................................................................................................. 33
Figure 3: Comparison between experimental and calculated surfaces tensions for
cyclohexane and toluene. ......................................................................................... 33
Figure 4: Comparison between experimental surface tensions and calculated ones
for Nitrogen ............................................................................................................... 34
Figure 5: Experimental and predicted surface tension for ethane using PC-SAFT-
EOS with Eq. 101. .................................................................................................... 35
Figure 6: Experimental and predicted surface tension for n-decane using PC-SAFT-
EOS with Eq. 101. .................................................................................................... 35
Figure 7: Comparison of experimental and calculated surface tensions of acetone
with PCP-SAFT-EOS and PC-SAFT-EOS ................................................................ 36
Figure 8: Comparison of experimental and calculated surface tension of
chloromethane using PCP-SAFT-EOS. .................................................................... 37
Figure 9: Comparison between calculated liquid volumes of CO2 using PCP-SAFT
and PC-SAFT with experimental data . .................................................................... 38
Figure 10: Experimental and calculated surface tension of CO2 using PC-SAFT-EOS
and PCP-SAFT-EOS ................................................................................................ 38
Figure 11: Experimental and calculated (PCP-SAFT-EOS-4C; PCP-SAFT-EOS-2B)
liquid volumes of water. ............................................................................................ 40
Figure 12: Experimental and calculated (PC-SAFT-EOS with 4C) free monomer mole
fraction of water. ....................................................................................................... 40
Figure 13: Experimental and calculated surface tension (PC-SAFT-EOS with 2B and
PC-SAFT-EOS with 4C) of water. ............................................................................. 41
Figure 14: Density profiles for pure water at different temperatures. ........................ 42
Figure 15: Comparison between literature molar volumes and calculated values of
SO3 with the parameters from Table 5. ..................................................................... 43
Figure 16: Experimental and calculated surface tension of sulphur trioxide. ............ 43
Figure 17: Comparison between literature molar volumes and calculated values with
PC-SAFT and PCP-SAFT for SO2 with the parameters from Table 6. ..................... 44
Figure 18: Experimental and calculated surface tension (PC-SAFT and PCP-SAFT)
of sulphur dioxide. .................................................................................................... 45
Figure 19: Comparison between literature densities and calculated values from PCP-
SAFT for H2S. ........................................................................................................... 46
Figure 20: Comparison between experimental surface tensions from PCP-SAFT for
H2S. .......................................................................................................................... 47
Figure 21: VLE of the system methane + n-heptane. ............................................... 49
Figure 22: Comparison between experimental and calculated surface tensions for
different methane+ n-alkane mixtures. ..................................................................... 49
Figure 23: VLE for the system Nitrogen + n-hexane. ................................................ 53
Figure 24: VLE for the system Nitrogen + n-heptane................................................ 54
Figure 25: VLE for the system Nitrogen + n-decane. ................................................ 54
Figure 26: Dependency of the binary interaction parameter to the number of carbons
in a chain for Nitrogen + n-alkane mixtures. ............................................................. 55
Loading more pages...