MULTI-SCALE, MULTI PHYSICS MODELING OF THERMO-CHEMICAL IRON/IRON OXIDE CYCLE FOR FUEL PRODUCTION By ABHISHEK KUMAR SINGH A DISSERTATION PRESENTED TO THE GRADUATE SCHOOL OF THE UNIVERSITY OF FLORIDA IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY UNIVERSITY OF FLORIDA 2013 1 © 2013 Abhishek Kumar Singh 2 To my parents and my brother 3 ACKNOWLEDGEMENTS First and foremost I would like to thank my family for always encouraging me to pursue knowledge, while being a constant support system during my successes and failures. I would like to thank Dr. Joerg Petrasch for guiding me throughout the course of my research by imparting his valuable knowledge and experience and Dr. James Klausner for providing me with all the necessary inputs and resources needed to conduct my research efficiently. I also like to thank Dr. Renwei Mei for his contribution in my research. I would like to express my gratitude towards Dr. David Hahn and Dr. Helena Weaver for being on my committee. I would also take the opportunity to acknowledge the efforts of Like Li, Amay Berde, Fotouh Al. Raqoum , Nima Rahamatani and Nick AuYeung for their contribution in my research in the form of experimental results and creative inputs. Lastly, special thanks to my lab mates at the Energy Park, especially Anupam Akolker and Midori Takagi for making the last four years a memorial experience 4 TABLE OF CONTENTS Page ACKNOWLEDGEMENTS ............................................................................................... 4 LIST OF TABLES ............................................................................................................ 8 LIST OF FIGURES .......................................................................................................... 9 NOMENCLATURE ........................................................................................................ 15 ABSTRACT ................................................................................................................... 16 CHAPTER 1 INTRODUCTION .................................................................................................... 18 2 SYSTEM MODEL FOR A HYDROGEN PRODUCTION PLANT ............................ 24 2.1 Hydrogen Production Process Overview .......................................................... 24 2.2 Mathematical Model .......................................................................................... 26 2.3 Syngas Production from the Gasifier ................................................................ 28 2.4 Results and Discussion ..................................................................................... 29 2.4.1 Energy Balance of the System .............................................................. 29 2.4.2 System Layout ....................................................................................... 30 2.5 Comparison of the Hydrogen Production Plants Using Iron/Iron Oxide Looping Cycle and the Conventional Process .................................................. 32 2.5.1 Plant Configuration ................................................................................ 34 2.5.2 Efficiency Comparison ........................................................................... 35 2.6 Summary .......................................................................................................... 36 3 THERMODYNAMIC ANALYSIS OF THE IRON/IRON OXIDE CYCLE .................. 47 3.1 Iron/Iron Oxide Looping Cycle Overview ........................................................... 47 3.2 Mathematical Model .......................................................................................... 49 3.3 Results and Discussion ..................................................................................... 49 3.3.1 Hydrogen Production Step ..................................................................... 49 3.3.1.1 Closed system analysis ............................................................ 49 3.3.1.2 Open system analysis ............................................................... 49 3.3.2 Reduction Step ...................................................................................... 50 3.3.2.1 Closed system .......................................................................... 50 3.3.2.2 Open system ............................................................................. 51 3.3.3 Effect of Iron Carbide Formation on Hydrogen Production .................... 51 3.3.4 Sulphur Present in Syngas .................................................................... 52 3.3.5 Cyclic Operation of the Reactor ............................................................. 53 3.3.6 Sulphur Laden Syngas .......................................................................... 53 3.4 Summary .......................................................................................................... 54 5 4 EXPERIMENTAL VALIDATION OF THE THERMODYNAMIC MODEL ................. 69 4.1 Thermodynamic Model Validation ..................................................................... 69 4.2 Mathematical Model .......................................................................................... 69 4.3 Results and Discussion ..................................................................................... 70 4.3.1 Comparison of the Theoretical Limit and the Experimental Hydrogen Production ............................................................................................. 70 4.3.1.1 Experimental facility .................................................................. 70 4.3.1.2 Description of experiments ....................................................... 72 4.3.1.3 Error analysis ............................................................................ 73 4.3.1.4 Comparison results ................................................................... 74 4.3.2 Comparison of the Theoretical Limit and the Experimental Magnetite Reduction Process ................................................................................. 77 4.3.2.1 Experimental facility .................................................................. 77 4.3.2.2 Comparison results ................................................................... 78 4.4 Summary .......................................................................................................... 81 5 WINDOWLESS HORIZONTAL CAVITY REACTOR MODELING .......................... 98 5.1 Solar Thermochemical Fuel Production ............................................................ 98 5.2 Radiation Model .............................................................................................. 100 5.3 Radiation in the Porous Media Inside the Absorbers ...................................... 103 5.4 Convective Heat Transfer ............................................................................... 104 5.5 Conductive Heat Transfer ............................................................................... 104 5.6 Chemical Reaction Rate ................................................................................. 104 5.7 Lattice Boltzmann Simulation inside Absorbers .............................................. 105 5.8 Process Flow .................................................................................................. 105 5.9 Results and Discussion ................................................................................... 105 5.10 Summary ...................................................................................................... 108 6 RADIATION MODELING ...................................................................................... 123 6.1 Radiative Heat Transfer in Porous Media ....................................................... 123 6.2 Monte Carlo Ray Tracing Model ..................................................................... 124 6.3 Diffusion Approximation .................................................................................. 127 6.4 P1- Approximation ........................................................................................... 127 6.5 Radiative Properties ........................................................................................ 128 6.6 Comparison of Different Radiation Models ..................................................... 130 7 COUPLED MODEL ............................................................................................... 132 7.1 Reactive Flows in Porous Media ..................................................................... 132 7.2 Mathematical Modeling ................................................................................... 133 7.3 Reaction Rate ................................................................................................. 135 7.4 Numerical Methods ......................................................................................... 136 7.4.1 Random Walk Transport ...................................................................... 136 7.4.2 Conduction .......................................................................................... 137 6 7.4.3 Fluid Flow ............................................................................................ 138 7.4.4 Radiation ............................................................................................. 138 7.5 Results ............................................................................................................ 139 7.5.1 Temperature Effect .............................................................................