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Non-Catalytic Production of Hydrogen Via Reforming of Diesel, Hexadecane and Bio-Diesel for Nitrogen Oxides Remediation

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Non-Catalytic Production of Hydrogen Via Reforming of Diesel, Hexadecane and Bio-Diesel for Nitrogen Oxides Remediation NON-CATALYTIC PRODUCTION OF HYDROGEN VIA REFORMING OF DIESEL, HEXADECANE AND BIO-DIESEL FOR NITROGEN OXIDES REMEDIATION DISSERTATION Presented in Partial Fulfillment of the Requirements for the Degree Doctor of Philosophy in the Graduate School of The Ohio State University By Sergio Manuel Hernandez Gonzalez, M.S., B.S. ***** The Ohio State University 2008 Dissertation Committee: Approved by Professor Yann Guezennec, Adviser Professor Vish Subramaniam, Co-adviser Adviser Professor Giorgio Rizzoni Graduate Program in Dr. Shawn W. Midlam-Mohler Mechanical Engineering Professor Junmin Wang © Copyright by Sergio Manuel Hernandez Gonzalez 2008 ABSTRACT After-treatment technologies are required for diesel engines to meet the current and future stringent emissions regulations. Lean NOx traps and SCR catalysts represent the major routes for after-treatment for NOx mitigations under lean exhaust conditions. These technologies require active agents (H2, CO and several hydrocarbons) that ei- ther participate in nitrogen oxide reduction reactions or regenerate the NOx storage sites. Nevertheless, these species have to be obtained from either the on-board fuel or additional sources such as urea. Hydrocarbons are seen thus far as the most reli- able source for generation of hydrogen. This work focuses then on the generation of hydrogen through Partial Oxidation of heavy hydrocarbons. The research is first oriented to assess numerically, using a proprietary code, the feasibility of the non-catalytic reforming of hexadecane (C16H34 a heavy hydrocarbon molecule used as a proxy for diesel fuel) under different conditions of equivalence ratio, steam to carbon ratio, and inlet temperatures. The reforming process is then analyzed within the characteristic quantities ranges: 1 ≤ φ ≤ 1.9, 0 ≤ S/C ≤ 2, 1000 ≤ Tini ≤ 1750 K. A novel contribution to the scientific community is the assessment of addition of water through secondary injection to improve the hydrogen production. Of special interest for automotive applications is the use of exhaust as a possible source for oxygen since diesel engines are operated under lean conditions. Such a concept is also studied ii numerically in this dissertation. A discussion on the kinetic mechanisms producing and consuming hydrogen in the partial oxidation of hexadecane is also included in this dissertation. Based upon the results obtained in the numerical simulation, a proof of concept of the POx of hexadecane is experimentally performed. Diesel fuel POx reforming is also experimentally studied since this concept is aimed to be utilized for diesel engine after-treatment. Bio-diesel has become very popular due to its chemical configuration containing simple chains and its lower pollution characteristic and its renewability as a bio-fuel. Hence, this research presents a novel study of partial oxidation of bio-diesel (B-100) to generate hydrogen or syngas. The results obtained using the 0D model strongly indicate that H2, CO and total hydrocarbons concentrations increase with increasing equivalence ratio (φ) for all tem- peratures and both sources of oxygen (air and lean exhaust). The three fuels tested experimentally showed an increasing H2 concentration with φ as well. Nevertheless, H2 and CO saturate due to the decreasing adiabatic flame temperature (Tad) with in- creasing equivalence ratio. Vapor addition slightly increases the H2 % Vol for low φ ratios, while it caused the H2 concentration to saturate at a faster rate as φ increased. Increasing Tini yields higher H2 concentrations owing to the higher Tad for all φ and S/C ratios. High H2 yields ( 25-30%) can be obtained for φ ≥ 1.6 for the low tem- ¬ perature case (1000 K), while even higher yields ( 30-40%) are seen for the high inlet ¬ temperature cases (1750 K). Addition of vapor along with the main feeds is beneficial at high inlet temperatures, while secondary injection of water showed a very slight increase in H2 concentration even if injected at high temperatures. However, as S/C is increased, a slower H2 saturation rate is seen for post-injection of vapor than for iii its equivalent main injection of vapor. Lower product composition are obtained using exhaust gas as O2 provider due to the lower flame temperature caused by the amount of present diluent in the stream. In summary, this study has demonstrated the feasibility of producing hydrogen-rich syngas from the partial oxidation of diesel fuel in a simple, practically implementable device which could be integrated into an on-board, after-treatment system for diesel engine vehicles. The system is capable of hydrogen yields consistent with the NOx reduction needs of current engines and does not require any additional fluids besides the engine fuel. The detailed 0D kinetics simulations in this study have served to understand the chemical kinetic mechanisms at play and, while not truly predictive, to provide invaluable design guidelines for practical implementations, particularly with respect to operating point equivalence ratio and the dominant role of temperature in maximizing the hydrogen yield. iv ACKNOWLEDGMENTS I would like to extend my gratitude to my adviser Dr. Yann Guezennec, for his contributions throughout the research, to my co-adviser Dr. Vish Subramaniam for our discussions on chemical kinetics and everything referent to the numerical simulation, and specially to Dr. Shawn Midlam-Mohler for his constant interest, comments and revisions throughout this work. Furthermore, I would like to thank the professors of the Mechanical Engineering Department who took me under their guidance during these years. I am indelibly grateful to Ranjit Annamalai and Zhijun Zou for providing many of the tools to develop this research. Special appreciation is also given to Kenny Follen for his constant advice on the development of this work and availability for language corrections, and mostly on my daily life, thanks for being an excellent friend. It is appropriate to thank Tenneco Inc. and the team that financially sponsored this project for giving me the opportunity to enjoy and grow professionally through this experience. I also thank the National Council of Science and Technology of Mexico (CONACyT, for its acronym in Spanish) for its sponsorship to carry out this research for the first years of the program. Special thanks are delivered to the staff at CAR for providing me with a nice envi- ronment and the facilities to develop this work. Specially to Mr. Don Williams who is an excellent machinist who not only understood every single drawing I produced but v also provided advice to enhance it. My fellow graduate and undergraduate students that contributed directly or indirectly on this project with ideas, thoughts, laughs and gatherings: Dr. Marcello Canova, Simone Bernasconi, Josh Supplee, Christopher Hoops and Orlando Inoa. I would like to extend my deepest thanks to my friends who have contributed much towards the enjoyment of my time in Columbus. It would be unfair to mention a few and leave others out of the list, everyone has given me something very special. Special gratitude is extended to Joana Ferreti with whom I shared a big part of this time and who always motivated me to continue on the search of answers in every aspect of my life. Finally and most important, I would like to strongly thank my family who has been there in every single moment of this journey for its patience and understanding. Thanks to my parents who provided me with the means and curiosity to pursue edu- cation and embrace my professional career. Also, my brother and sister who listened to my ideas always. They know the journey has not been easy on the personal side but they were always accompanying me no matter the time of the day or night. Last but not least, special gratitude is extended to my uncle Abel Hernandez who always encouraged me to go beyond limitations and to pursue advanced education. vi VITA October 8, 1978 . Born - Salamanca, Guanajuato, Mexico 2001 . B.S. Mechanical Engineering Universidad de Guanajuato Guanajuato, Mexico 2003 . M.S. Mechanical Engineering University of Manchester Institute of Science and Technology Manchester, United Kingdom 2004 to present . .Graduate Research Associate Mechanical Engineering The Ohio State University Center for Automotive Research United States of America FIELDS OF STUDY Major Field: Mechanical Engineering vii TABLE OF CONTENTS Page Abstract ........................................ ii Acknowledgments ................................... v Vita .......................................... vii List of Figures .................................... xiv List of Tables ..................................... xxii Chapters: 1. Introduction ................................... 1 1.1 Introduction ............................... 1 1.2 Motivation ................................ 2 1.3 Thesis Outline .............................. 4 2. Literature Review ................................ 8 2.1 Introduction ............................... 8 2.2 After-Treatment Technologies ...................... 10 2.2.1 Lean NOx Traps, LNT ...................... 13 2.2.2 Hydrocarbon-Selective Catalytic Reaction Systems, HC-SCR . 18 viii 2.2.3 Urea/Ammonia-Selective Catalytic Reaction, Urea/NH3-SCR 23 2.2.4 Hydrogen-Selective Catalytic Reaction, H2-SCR ........ 30 2.2.5 Plasma Assisted Catalytic Removal of NOx .......... 35 2.3 Fuel Reforming Technologies ...................... 36 2.3.1 Catalytic Reforming ....................... 38 2.3.1.1 Steam Reforming, SR .................. 39 2.3.1.2 Partial Oxidation Reforming,
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