Aromatic Hydrocarbon Sampling and Extraction From Flames Using Temperature-Swing ...

207 Pages·2010·9.88 MB·English

Aromatic Hydrocarbon Sampling and Extraction From
Flames Using Temperature-Swing Adsorption/Desorption
Processes
by
Hei Ka Chan
A thesis submitted in conformity with the requirements
for the degree of Master of Applied Science
Graduate Department of Mechanical and Industrial Engineering
University of Toronto
Copyright (cid:13)c 2011 by Hei Ka Chan
Abstract
Aromatic Hydrocarbon Sampling and Extraction From Flames Using
Temperature-Swing Adsorption/Desorption Processes
Hei Ka Chan
Master of Applied Science
Graduate Department of Mechanical and Industrial Engineering
University of Toronto
2011
The measurement of Polycyclic Aromatic Hydrocarbons (PAHs) in flames is essen-
tial for the understanding of soot formation. In comparison to conventional aromatics-
samplingtechniques,anewtechniquewasproposedthatinvolvesfewermanualoperations
and no hazardous extraction solvents. Apparatus and experimental procedures of the
newly proposed adsorptive-sampling and desorptive-extraction technique for aromatic-
hydrocarbon measurements were established in this study. The capabilities and lim-
itations of this new technique were assessed in terms of limits of detection, sampling
locations and data repeatability.
The accuracy of this technique was also evaluated. Aromatic-hydrocarbon species
concentrations were measured in laminar co-flow diffusion flames of ethylene (C H ) and
2 4
synthetic paraffinic kerosene (SPK). The results obtained from the ethylene flame were
compared to its numerical simulation, with the goal of achieving agreement within an
order of magnitude. The differences between simulated values and experimental mea-
surements, along with the limitations of the technique, were used as an indication of the
accuracy of the technique.
ii
Acknowledgements
I owe the deepest gratitude to my supervisor, Professor Murray Thomson, who has sup-
portedmethroughoutthecourseofthisthesiswithhispatience, guidanceandknowledge.
Without his encouragement, this thesis would have never been written or completed, and
one simply could not wish for a friendlier advisor. I would also like to thank Dr. Seth
Dworkin, who provided his generous help on running the numerical models and numer-
ous valuable insights to my endeavours in this study. Parham Zabeti is a key member
in my research group who I could never thank enough. His support on the setup of the
experimental apparatus and help when I had troubles in my experiments are heartily
appreciated.
This study has also benefited from the valuable advices offered by Mr. Dan Mathers
and Ms. Ying Lei from the Analytical lab for Environment Science Research and Training
at the University of Toronto. I also want to show my appreciation to Prof. Jim Wallace
and Prof. Greg Evans for being members on my thesis defense committee.
Thanks to every member in the Combustion Research Group of M.I.E. at the Uni-
versity of Toronto, specifically Meghdad Saffaripour, Coleman Young and Dr. Subram
M. Sarathy, for the quality time we spent together. This study would be more difficult
without their support.
Finally, I would like to show my gratefulness to my family members. I thank them
for taking off so many of my responsibilities at home so that I could fully concentrate on
my academic work.
iii
Contents
Abstract ii
Acknowledgements iii
Table of Contents iv
List of Tables ix
List of Figures xv
Acronyms xvi
1 Introduction 1
1.1 Research Motivation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
1.2 Dissertation Objectives . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
2 Background 4
2.1 Fuels in Experiments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
2.1.1 Ethylene . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
2.1.2 Shell Gas-to-Liquids Synthetic Jet Fuel (GTL-SJF) . . . . . . . . 5
2.2 Polycyclic Aromatic Hydrocarbons (PAHs) and Their Effects . . . . . . . 9
2.3 Chemical Pathways: From Fuel to PAHs to Soot . . . . . . . . . . . . . . 12
2.3.1 From Fuel to the First Aromatic Ring . . . . . . . . . . . . . . . 12
iv
2.3.1.1 Oxidation of Alkanes (Paraffins) . . . . . . . . . . . . . 12
2.3.1.2 Oxidation of Alkenes (Olefins) . . . . . . . . . . . . . . . 13
2.3.1.3 Formation of the First Aromatic Ring . . . . . . . . . . 15
2.3.2 From 1-Ring Aromatic Hydrocarbons to PAHs to Soot . . . . . . 16
2.3.2.1 Formation of PAHs . . . . . . . . . . . . . . . . . . . . . 16
2.3.2.2 Formation of Soot . . . . . . . . . . . . . . . . . . . . . 17
2.4 Co-flow Burner & Numerical Modeling . . . . . . . . . . . . . . . . . . . 21
2.4.1 Co-flow Diffusion Flame and Burner . . . . . . . . . . . . . . . . 21
2.4.2 Brief Description of the Numerical Model for the Ethylene Flame 23
2.5 Conventional & Proposed Techniques of PAH Measurement . . . . . . . . 23
2.5.1 Conventional Techniques of PAH Measurement in Flames . . . . . 23
2.5.2 Newly Proposed Technique for PAH Measurement in Flames . . . 31
2.5.2.1 Thermal Adsorption/Desorption Processes . . . . . . . . 31
2.5.2.2 Working Principle of Thermal Adsorption/Desorption . 33
3 Experimental Apparatus and Methodology 42
3.1 Co-flow Diffusion Burner and its Peripheral Equipment . . . . . . . . . . 42
3.1.1 Co-flow Diffusion Burner Setup . . . . . . . . . . . . . . . . . . . 42
3.1.2 Peripheral Equipment . . . . . . . . . . . . . . . . . . . . . . . . 45
3.1.2.1 Ethylene Flame . . . . . . . . . . . . . . . . . . . . . . . 45
3.1.2.2 Shell GTL-SJF Flame . . . . . . . . . . . . . . . . . . . 48
3.2 Gas-sampling System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52
3.2.1 Sampling Probe . . . . . . . . . . . . . . . . . . . . . . . . . . . 52
3.2.2 Other Components along the Sampling Path . . . . . . . . . . . . 54
3.3 Sampling Procedures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55
3.3.1 Preliminary Steps . . . . . . . . . . . . . . . . . . . . . . . . . . . 55
3.3.2 Flame Sampling . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59
3.3.3 Dynamic Headspace Adsorption Sampling . . . . . . . . . . . . . 62
v
3.4 Analytical Procedures . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64
3.4.1 PreliminaryCompoundIdentificationandStandard-SolutionPrepa-
ration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66
3.4.2 FID-Signals/Compound-Mass Calibration . . . . . . . . . . . . . 68
3.4.3 Sample Extraction by Thermal Desorption . . . . . . . . . . . . . 74
3.4.3.1 Pneumatic Adjustments . . . . . . . . . . . . . . . . . . 75
3.4.3.2 Trap Cleaning . . . . . . . . . . . . . . . . . . . . . . . 76
3.4.3.3 Thermal Desorption Method . . . . . . . . . . . . . . . . 77
3.4.4 Gas Chromatograph Method . . . . . . . . . . . . . . . . . . . . . 79
3.4.5 Determination of Concentrations of Target Aromatics from Exper-
imental Samples . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81
3.4.5.1 Compound Identification . . . . . . . . . . . . . . . . . . 82
3.4.5.2 Compound Quantification . . . . . . . . . . . . . . . . . 84
3.4.6 Summary of the Determination of Species Concentrations . . . . 84
3.5 Adsorbent Rejuvenation . . . . . . . . . . . . . . . . . . . . . . . . . . . 86
4 Technique Capabilities and Validation 91
4.1 Validity of Chromatographic Data . . . . . . . . . . . . . . . . . . . . . . 91
4.1.1 Concentration-dependent Drifting of Retention Times . . . . . . . 92
4.1.2 Signal-to-noise Ratio . . . . . . . . . . . . . . . . . . . . . . . . . 97
4.1.3 Analyte Co-elution . . . . . . . . . . . . . . . . . . . . . . . . . . 97
4.2 Limits of Detection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 104
4.3 Effects of Cartridge Placement . . . . . . . . . . . . . . . . . . . . . . . . 106
4.4 Adsorbent Breakthrough Volumes (BTVs) . . . . . . . . . . . . . . . . . 111
4.4.1 BTV Determination by Dynamic Headspace Sampling . . . . . . 112
4.4.2 BTV Determination by Flame Sampling . . . . . . . . . . . . . . 115
4.5 Linearity of Samples . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 118
4.6 Statistical Analysis of Experimental Data . . . . . . . . . . . . . . . . . . 124
vi
4.6.1 Repeatability of Adsorptive Sampling in a Dynamic Headspace . . 125
4.6.2 Repeatability of Flame-Aromatics Adsorption . . . . . . . . . . . 126
5 Results and Discussion 128
5.1 Results for the Ethylene Flame . . . . . . . . . . . . . . . . . . . . . . . 128
5.2 Results for the GTL-SJF Flame . . . . . . . . . . . . . . . . . . . . . . . 133
6 Closure 135
6.1 Summary and Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . 135
6.2 Recommendations and Future Works . . . . . . . . . . . . . . . . . . . . 137
7 Bibliography 140
8 Appendices 149
8.1 Appendix I—Composition Analysis of SPK Fuels . . . . . . . . . . . . . 150
8.2 Appendix II—Governing Equations of Diffusion Flames . . . . . . . . . . 151
8.2.1 Governing Equations of Diffusion Flames . . . . . . . . . . . . . . 151
8.2.2 Flame-Height Prediction . . . . . . . . . . . . . . . . . . . . . . . 155
8.3 Appendix III—Calculations for the flow conditions of the fuel/oxidizer
streams of the ethylene flame . . . . . . . . . . . . . . . . . . . . . . . . 157
8.4 Appendix IV—Engineering drawings of custom-built parts . . . . . . . . 159
8.5 Appendix V—Thermal Adsorption/Desorption Processes . . . . . . . . . 168
8.6 Appendix VI—Gas Chromatography . . . . . . . . . . . . . . . . . . . . 177
8.7 Appendix VII—Example of a Typical TD Sequence . . . . . . . . . . . . 183
8.8 Appendix VIII—Sample Chromatograms . . . . . . . . . . . . . . . . . . 186
8.9 Appendix IX—Additional Graphs . . . . . . . . . . . . . . . . . . . . . . 189
vii
List of Tables
2.1 Physiochemical properties of ethylene [9] . . . . . . . . . . . . . . . . . . 5
2.2 Chemical composition of Shell’s GTL-SPK fuel . . . . . . . . . . . . . . . 7
2.3 Advantages and disadvantage of SPK blend [17] . . . . . . . . . . . . . . 8
2.4 LIF detection limits (LODs) for selected PAHs with a signal-to-noise ratio
of 2 [35] . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
2.5 Definitions of some frequent terms used in the description of adsorptive
behaviours [51] . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
2.6 Typical applications of some common adsorbents [51] . . . . . . . . . . . 35
2.7 Properties of Tenax TA [53] . . . . . . . . . . . . . . . . . . . . . . . . . 37
3.1 Flow rates and pressures of the fuel and oxidizer for the ethylene flame . 46
3.2 Summary of the flow rates of fuel, oxidizer, fuel diluent and sampling
stream in the ethylene- and SPK-flame-sampling experiments . . . . . . . 60
3.3 Chemical compositions of the aromatic mixture and the standard solution
used for calibration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68
3.4 Summary of the parameters used in the TD & GC methods; refer to Table
8.15 for the functions of the TD method parameters . . . . . . . . . . . . 87
4.1 Summary of the 4 target aromatic hydrocarbon species studied . . . . . . 94
viii
4.2 Drifting of retention times when aromatic compounds existed in different
combinationsandamountswerecollectedfromtheethyleneflameandsent
to the FID . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 96
4.3 Limits of detection for various aromatic hydrocarbon compounds in num-
ber of nmoles (10−9 mol) . . . . . . . . . . . . . . . . . . . . . . . . . . . 104
4.4 Limitsofdetectionforvariousaromatichydrocarboncompoundsexpressed
in concentrations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 106
4.5 Repeatability of the data obtained from dynamic headspace sampling; n is
number of moles collected, X is mole fraction, and the subscripts represent
species . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 126
4.6 Averaged mole fractions (in ppm) of benzene and naphthalene, and their
standard deviations measured at various locations of the ethylene flame . 127
6.1 Summary of the 4 target aromatic hydrocarbon species studied (repeated) 136
ix
List of Figures
2.1 Chemical structure of ethylene, C H . . . . . . . . . . . . . . . . . . . . 5
2 4
2.2 Gas-to-Liquids process of natural gas; SPK is one of the final products. . 6
2.3 Reduction in the emission of particulate matters from 2 military gas tur-
bines burning various SPK blends . . . . . . . . . . . . . . . . . . . . . . 8
2.4 Typical emissions of PAHs by sectors [25] . . . . . . . . . . . . . . . . . . 10
2.5 Names and structures of selected PAHs monitored under EPA and EU
regulations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
2.6 Formation of first ring from acetylene [27] . . . . . . . . . . . . . . . . . 15
2.7 HACA mechanism of PAH formation [27] . . . . . . . . . . . . . . . . . . 16
2.8 Condensation process that leads to PAH growth [27] . . . . . . . . . . . 17
2.9 Typical locations of soot formation in a diffusion flame [30] . . . . . . . . 18
2.10 A schematic of PAH and soot formation in non-premixed flames [27] . . . 20
2.11 Over- and under-ventilated flames in a co-flow burner; r is the fuel-tube
i
radius, r is the annulus radius and z is the flame height [26] . . . . . . 22
o f
2.12 Comparison of model predictions on PAH concentrations for a premixed
ethylene flame and the experimental data obtained by on-line microprobe-
sampling/GC/MS [44] . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
2.13 ComparisonofmodelpredictionsonPAHconcentrationsforacounter-flow
diffusion ethylene flame and the experimental data obtained by on-line
microprobe-sampling/GC/MS [45] . . . . . . . . . . . . . . . . . . . . . . 28
x