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Polycyclic Aromatic Hydrocarbons Formation and Pyrolysis

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Polycyclic Aromatic Hydrocarbons Formation and Pyrolysis UNIVERSITY OF CINCINNATI Date:___________________ I, _________________________________________________________, hereby submit this work as part of the requirements for the degree of: in: It is entitled: This work and its defense approved by: Chair: _______________________________ _______________________________ _______________________________ _______________________________ _______________________________ A Study of the Pyrolysis of Tire Derived Fuels and an Analysis of Derived Chars and Oils A dissertation submitted to the Division of Research and Advanced Studies of the University of Cincinnati in partial fulfillment of the requirements for the degree of DOCTORATE OF PHILOSOPHY (PhD.) in the Department of Civil and Environmental Engineering of the College of Engineering 2006 by Kessinee Unapumnuk B.S. Rural Technology Thammasat University, Thailand, 1996 M.S. Environmental Management and Technology Asian Institute of Technology, Thailand, 1999 Committee Chair: Professor Timothy C. Keener, PhD., PE, QEP ABSTRACT In this research, the pyrolysis product distribution rates and pyrolysis behavior of tire derived fuels (TDF) were investigated using thermogravimetric (TGA) techniques. A TGA was designed and built in order to investigate the behavior and products of pyrolysis of typical TDF specimens. Fundamental knowledge of thermogravimetric analysis and principal fuel analysis is applied in this study. Thermogravimetry of the degradation temperature of the TDF confirms the overall decomposition rate of the volatile products during the depolymerization reaction. The principal fuel analysis (proximate and ultimate analysis) of the pyrolysis char products shows the correlation of volatilization into the gas and liquid phases and the existence of fixed carbon and other compounds that remain as a solid char. The kinetic parameters were calculated using least square with minimizing sum of error square technique. The results show that the average kinetic parameters of TDF are the activation energy, E = 1322 ± 244 kJ/mol, a pre-exponential constant of A= 2.06 ± 3.47 x 1010 min-1, and a reaction order n = 1.62 ± 0.31. The model-predicted rate equations agree with the experimental data. The overall TDF weight conversion represents the carbon weight conversion in the sample. Three commercially important pyrolysis by-products from vehicle tires are liquid oil, solid char, and exhaust gas. These products could be contaminated by volatile toxic compounds released from the tire structure before combustion. The release of volatile materials from the tire structure during pyrolysis offers the greatest potential for separation of these compounds from the evolved gases and vapors, as the concentrations of these species are at their greatest in the vapor phase during this period. The influences of heating rate and pyrolysis temperature were investigated. The temperature was studied from 325 to 1000 oC, a range where substantial devolatilization occurs. The results showed that the heating rate and the pyrolysis temperature were the key factors in determining the two pyrolysis yields: condensed oil and gas product. However, the overall desulfurization of the pyrolysis reaction was essentially unaffected by the heating rates. Products from the pyrolysis of TDF were investigated with various analytical techniques and under various maximum pyrolysis temperatures and heating rates. The pyrolysis products are classified as char (solid product), pyrolytic oil (liquid) and gas. Principle functional groups of the TDF and pyrolytic oil were confirmed by Fourier Transform Infrared Spectrometer, coupled with attenuated total reflectance (FT-IR/ATR). The components of the pyrolytic oil fraction were individually quantified using gas chromatography coupled with mass spectrometry (GC-MS). The major products are one- and two-ring methyl-substituted aromatic isomers. By-product formation mechanisms of TDF pyrolysis were hypothesized based on the products identified. The mechanisms for aromatic hydrocarbon formation were found to be associated with polymer degradation, methyl displacement, and the Diels-Alder reactions. Our study indicated that GC-MS coupled with FT-IR is sufficient to investigate the semi-volatile and volatile organic species from complex polymeric materials such as tires. ACKNOWLEDGEMENT I would like to thank the following people who helped to make this dissertation possible: My advisor, Dr. Tim C. Keener, for his valuable guidance, patience, constructive challenges and encouragement throughout my study. My co-advisor, Dr. Mingming Lu, for her effort to advice and criticize my work especially on the chromatography laboratory analysis. My dissertation committee members, Dr. George Sorial and Dr. Soon-Jai Khang, for their kindly advice on my research. I feel truly appreciated to have had such distinguished mentors directing this academic process. My special colleagues during doctoral study, Phirun, Jun, Fuyan, Jacob, Pamela, Sang- Sup, Ricardo, Sook and Shuang for their encouragement and support energized my hopes and which whom I shared so many experiences. I would like to thank all Thai friends: Dr. Sumana, Dr. Supa, Phirun, Atchara, Wassana, Chaichana, and Sarawuth who have made Cincinnati quite an enjoyable city for me during the past 4 years. The Royal Thai Government for a scholarship that allowed me to pursue a degree in the United States. My loving family for their encouragement, support and numerous sacrifices. Especially, my mother for her unconditional love, who cry and laugh with me everyday for years. My two sisters, who have been taking good care of my mother while I concentrated on completing the degree. Lastly, I dedicate my work to my beloved passed away father without his loving spirit I would not have indeed come this far. His loving spirit were a continual source of inspiration to me. TABLE OF CONTENTS TABLE OF CONTENTS.....................................................................................................I LIST OF TABLES............................................................................................................ IV LIST OF FIGURES ........................................................................................................... V NOMENCLATURE ........................................................................................................VII 1 Chapter 1 Introduction ................................................................................................ 1 1.1 Background and Problem Statement................................................................... 1 1.2 Research Objectives............................................................................................ 4 1.3 Literature Review................................................................................................ 5 1.3.1 Properties of Tires....................................................................................... 6 1.3.2 Combustion of Tires ................................................................................... 9 1.3.3 Pyrolysis Mechanism of Tires.................................................................... 9 1.3.4 Formation of Polycyclic Aromatic Hydrocarbons.................................... 11 1.4 References......................................................................................................... 14 2 Chapter 2 Research Methodology............................................................................. 18 2.1 Properties of Tire Derived Fuel Materials ........................................................ 18 2.2 Experimental Design......................................................................................... 19 2.2.1 Reactor Design.......................................................................................... 19 2.2.2 Pyrolysis Product Distribution Experiment .............................................. 23 2.2.3 Proximate and Ultimate analysis .............................................................. 23 2.2.4 Identification of Organic Compounds ...................................................... 23 2.3 References......................................................................................................... 31 3 Chapter 3 Thermogravimetric Study and Pyrolysis Kinetic Mechanisms................ 34 3.1 Abstract............................................................................................................. 34 I 3.2 Introduction....................................................................................................... 35 3.3 Experimental Method........................................................................................ 35 3.4 Results and Discussion..................................................................................... 36 3.4.1 Preliminary Experiments to Establish the Reactor Design Criteria.......... 36 3.4.2 Investigation of TDF Decomposition ....................................................... 39 3.4.3 Pyrolysis Kinetic Interpretation of Experimental Data............................. 43 3.4.4 Decomposition of TDF in Different Atmospheres ................................... 50 3.5 Conclusion ........................................................................................................ 52 3.6 References......................................................................................................... 53 4 Chapter 4 The Recovery of Pyrolysis By-products and the Removal of Sulfur....... 55 4.1 Abstract............................................................................................................
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