Chemical Looping Partial Oxidation Process for Syngas Production DISSERTATION Presented in Partial Fulfillment of the Requirements for the Degree Doctor of Philosophy in the Graduate School of The Ohio State University By Dikai Xu Graduate Program in Chemical Engineering The Ohio State University 2017 Dissertation Committee: Liang-Shih Fan, Advisor, David Wood, Barbara Wyslouzil, and Jacques Zakin Graduate Faculty Representative: Esperanza Carcache de Blanco Copyrighted by Dikai Xu 2017 Abstract The chemical looping partial oxidation process is developed for the efficient conversion of gaseous and solid fuels into syngas via partial oxidation. The chemical looping partial oxidation process converts the fuels into high purity syngas with flexible H2:CO ratio that is suitable for downstream fuel or chemical synthesis. In the chemical looping partial oxidation process, the fuels are partially oxidized in the reducer reactor by the oxygen carrier to generate high purity syngas. The reduced oxygen carrier is regenerated in a fluidized bed combustor via the oxidation reaction with air. Compared to the conventional syngas generation processes, the chemical looping partial oxidation process eliminates the need for additional steam or molecular oxygen from an air separation unit (ASU), resulting in an increased cold gas efficiency and decreased fuel consumption. The chemical looping partial oxidation process features the combination of an iron-titanium composite metal oxide (ITCMO) oxygen carrier and a co-current gas- solid moving bed reducer reactor. The ITCMO oxygen carrier is selected for the chemical looping partial oxidation process due to its desired thermodynamic and kinetic properties. Theoretical analysis aided by a modified Ellingham Diagram illustrates that syngas production is thermodynamically favored in the presence of ITCMO oxygen carrier. The co-current moving bed reducer design provides a desirable gas-solid contacting pattern that minimizes carbon deposition while maximizing the syngas yield. Experimental studies in a fixed bed reactor and a bench scale reactor successfully demonstrate the ii production of high purity syngas from methane and biomass with the combination of moving bed reducer and ITCMO oxygen carrier. Further scale-up of the chemical looping partial oxidation process is demonstrated in an integrated sub-pilot scale reactor system using non-mechanical gas sealing and solid circulation devices. A dynamic modeling scheme is developed for studying the transient behavior and the control of the chemical looping system. A hierarchical control system based on sliding mode control concept is developed for the chemical looping technologies to simplify process operation. iii Acknowledgments I would like to express my gratitude to all those who gave me the possibility to complete this thesis. I want to first thank my advisor Dr. Liang-Shih Fan for offering me the opportunity to pursue my degree at OSU. I was impressed and motivated by Dr. Fan’s enthusiasm for the research in our group. The unique research experience along with Dr. Fan’s tuition I received over the past five years will greatly benefit my future. The research group not only exposed me to the invaluable research experience, but also introduced mentors, collaborators, and friends to me. In particular, I want to thank Liang Zeng, Andrew Tong, and Siwei Luo for offering me the guidance and help on research. The work presented in this dissertation is, in part, inspired by the discussion with them. I greatly benefited from the discussions with my knowledgeable collaborators on various topics. For that I want to thank Lang Qin, Dawei Wang, Zhuo Cheng, Pengfei He, and Qiang Zhou from our research group, Umit Ozguner and Arda Kurt from OSU ECE Department, and Tom Flynn, Tim Fuller, Chris Poling, Luis Velazquez-Vargas, and Bill Arnold from Babcock & Wilcox. I am grateful to my all lab mates and friends, Tien- Lin Hsieh, Cheng Chung, Mandar Kathe, Ankita Majumdar, Sam Bayham, Aining Wang, Yitao Zhang, Mengqing Guo, Sourabh Nadgouda, Mingyuan Xu, Yaswanth Pottimurthy, Cody Park, Fanhe Kong, and Yu-Yen Chen, for their support in my research as well as my daily life. iv Vita July 2012 ........... B.S. Chemical Engineering, Tsinghua University, Beijing, China Publications Xu, D., Zhang, Y., Hsieh, T.-L., Guo, M., Qin, L., Chung, C., Fan, L.-S., & Tong, A. (2017). A Novel Chemical Looping Partial Oxidation Process for Thermochemical Conversion of Biomass to Syngas. In second review at Energy & Environmental Science. Luo, S., Zeng, L., Xu, D., Kathe, M., Chung, E., Deshpande, N., Qin, L., Majumder, A., Hsieh, T.-L., Tong, A., Sun, Z., & Fan, L.-S. (2014). Shale gas-to-syngas chemical looping process for stable shale gas conversion to high purity syngas with a H 2: CO ratio of 2: 1. Energy & Environmental Science, 7(12), 4104-4117. Qin, L., Cheng, Z., Fan, J. A., Kopechek, D., Xu, D., Deshpande, N., & Fan, L.-S. (2015). Nanostructure formation mechanism and ion diffusion in iron–titanium composite materials with chemical looping redox reactions. Journal of Materials Chemistry A, 3(21), 11302-11312. v Luo, S., Majumder, A., Chung, E., Xu, D., Bayham, S., Sun, Z., Zeng, L., & Fan, L.-S. (2013). Conversion of Woody Biomass Materials by Chemical Looping Process Kinetics, Light Tar Cracking, and Moving Bed Reactor Behavior. Industrial & Engineering Chemistry Research, 52(39), 14116-14124. Cheng, Z., Qin, L., Guo, M., Fan, J. A., Xu, D., & Fan, L.-S. (2016). Methane adsorption and dissociation on iron oxide oxygen carriers: the role of oxygen vacancies. Physical Chemistry Chemical Physics, 18(24), 16423-16435. Qin, L., Guo, M., Cheng, Z., Xu, M., Liu, Y., Xu, D., Fan, J. A., & Fan, L.-S. (2017). Improved cyclic redox reactivity of lanthanum modified iron-based oxygen carriers in carbon monoxide chemical looping combustion. Journal of Materials Chemistry A. DOI: 10.1039/C7TA04228K. Fields of Study Major Field: Chemical Engineering vi Table of Contents Abstract ....................................................................................................................... ii Acknowledgments...................................................................................................... iv Vita .............................................................................................................................. v Table of Contents ...................................................................................................... vii List of Tables .............................................................................................................. x List of Figures ............................................................................................................ xi Chapter 1: Introduction ............................................................................................... 1 The Production of Syngas ....................................................................................... 1 Chemical Looping Technologies ............................................................................ 6 Chemical Looping Combustion ........................................................................... 7 Chemical Looping Partial Oxidation ................................................................. 11 Chemical Looping Systems using Moving Bed Reactors ................................. 13 Chapter 2: Thermodynamics of Chemical Looping Partial Oxidation ..................... 17 Thermodynamics of Oxygen Carriers ................................................................... 17 Thermodynamics of the Iron-Titanium Composite Metal Oxide (ITCMO) ......... 27 vii Reactor Design Considerations ............................................................................. 31 Mass Balance and Thermodynamics in Moving Bed Reactors ............................. 38 Conclusion ............................................................................................................. 49 Chapter 3: Experimental Studies of Chemical Looping Partial Oxidation ............... 52 Reactivity of the ITCMO ...................................................................................... 52 Syngas Generation in a Fixed Bed Reactor ........................................................... 56 CH4 Partial Oxidation in a Moving Bed Reducer ................................................. 61 Solid Fuel Gasification in a Moving Bed Reducer ............................................... 70 Scale-up of Chemical Looping Partial Oxidation ................................................. 88 Sizing of Reactors .............................................................................................. 90 Design of the Sub-pilot Reactor System ............................................................ 92 Operation of the Sub-pilot Reactor System ....................................................... 99 Conclusion ........................................................................................................... 101 Chapter 4: Dynamic Simulation of Chemical Looping Systems ............................ 102 Physical Model .................................................................................................... 103 Components of the System .............................................................................. 103 Mass Balance ................................................................................................... 104 Pressure Balance and Hydrodynamics ...........................................................