CO2 (H2S) MEMBRANE SEPARATIONS AND WGS MEMBRANE REACTOR MODELING FOR FUEL CELLS DISSERTATION Presented in Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy In the Graduate School of the Ohio State University By Jin Huang, M. ***** The Ohio State University 2007 Dissertation Committee: Approved by Professor W. Winston Ho, Advisor Professor L. James Lee _____________________________________________________________________________ _ Advisor Professor Kurt W.
Koelling Graduate program in Chemical Engineering UMI Number: 3241691 UMI Microform 3241691 Copyright 2007 by ProQuest Information and Learning Company. All rights reserved. This microform edition is protected against unauthorized copying under Title 17, United States Code. ProQuest Information and Learning Company 300 North Zeeb Road P.
Box 1346 Ann Arbor, MI 48106-1346 ABSTRACT Acid-gas removal is of great importance in many environmental or energy-related processes. Compared to current commercial technologies, membrane-based CO2 and H2S capture has the advantages of low energy consumption, low weight and space requirement, simplicity of installation / operation, and high process flexibility. However, the large-scale application of the membrane separation technology is limited by the relatively low transport properties. In this study, CO2 (H2S)-selective polymeric membranes with high permeability and high selectivity have been studied based on the facilitated transport mechanism.
The membrane showed facilitated effect for both CO2 and H2S. A CO2 permeability of above 2000 Barrers, a CO2/H2 selectivity of greater than 40, and a CO2/N2 selectivity of greater than 200 at 100 – 150oC were observed. As a result of higher reaction rate and smaller diffusing compound, the H2S permeability and H2S/H2 selectivity were about three times higher than those properties for CO2. The novel CO2-selective membrane has been applied to capture CO2 from flue gas and natural gas.
In the CO2 capture experiments from a gas mixture with N2 and H2, a permeate CO2 dry concentration of greater than 98% was obtained by using steam as the sweep gas. In CO2/CH4 separation, decent CO2 transport properties were obtained with a feed pressure up to 500 psia. With the thin-film composite membrane structure, significant increase on the CO2 flux was achieved with the decrease of the selective layer thickness. ii With the continuous removal of CO2, CO2-selective water-gas-shift (WGS) membrane reactor is a promising approach to enhance CO conversion and increase the purity of H2 at process pressure under relatively low temperature.
The simultaneous reaction and transport process in the countercurrent WGS membrane reactor was simulated by using a one-dimensional non-isothermal model. The modeling results show that a CO concentration of less than 10 ppm and a H2 recovery of greater than 97% are achievable from reforming syngases. In an experimental study, the reversible WGS was shifted forward by removing CO2 so that the CO concentration was significantly decreased to less than 10 ppm. The modeling results agreed well with the experimental data.
iii Dedicated to my parents, my brother and Yujun for their love and support iv ACKNOWLEDGMENTS I would like to thank the following people for their help and support in conducting this research: • Dr. Winston Ho, my advisor at Ohio State, for his thoughtful guidance, enthusiastic discussion and continuous support and encouragement throughout the five years I have been in the United States. His persistence in pursuing the truth and his hard-working attitude have been, and will be, inspiring my career and life in the past and in the future. James Lee, Dr.
David Tomasko, and Dr. Barbara Wyslouzil for all their constructive critiques which helped me to improve my work. • I thank all my colleagues in Dr. Ho’s group: He Bai, Philip Chang, Bishnupada Mandal, Michael Vilt, Chi Yen, Jian Zou, and fellow students in Koffolt Labs who have to remain unnamed here.
Also I would like to thank the following people: • My friends, both in US and China, for all their encouragements and friendship. • My parents and my brother for their support and love throughout my studies over the years. v • Yujun for her support, encouragements, patience, and love while writing this thesis. vi VITA April 19, 1977.Born in Jianli, Hubei, China 1996.
Organic Chemical Technology, Wuhan Institute of Chemical Technology, Wuhan, China 1999. Chemical Engineering, East China Univ. of Science & Technology, Shanghai, China 2001 – 2002 .Graduate Research Associate, University of Kentucky, Lexington, KY, USA 2002 – 2006.Graduate Research Associate, The Ohio State University, Columbus, OH, USA PUBLICATIONS 1. Jin Huang, Louei El-Azzami, and W.
Winston Ho, “Modeling of CO2-selective Water- Gas-Shift Membrane Reactor for Fuel Cell,” J. Jian Zou, Jin Huang, and W. Winston Ho, “CO2-Selective Water gas shift Membrane Reactors for Fuel Cell Hydrogen Processing,” accepted by Ind. Ruofei Zhao, Jin Huang, Bin Sun, and Gance Dai, “A Study of Mechanical Properties of Mica Filled Polypropylene Based GMT Composites,” J.
Hui-ling Lu, Jin Huang, and Gance Dai, “Effects of Processing Parameters on Melt Impregnation of GMT Sheets,” J. East China Univ. Ming Li, Jin Huang, and Gance Dai, “Melt Flow through Glass Fiber Mat during GMT Melt Impregnation,” Acta Materiae Compositae Sinica, 17(3), pp. FIELDS OF STUDY Major Field: Chemical Engineering viii TABLE OF CONTENTS Abstract……………………………………………….vii List of Tables………………………….xiii List of Figures………………………………………………………………….xiv List of Notations……………………………………………………………….1 Membrane Separation Technology…………….2 Acid-gas Removal…………….3 Scope and Objectives of Research……………………………………………….
Synthesis of CO2 (H2S)-Selective Membrane……………….1 Polymeric Membrane for Gas Separation………………………………….2 Reaction Mechanism between Amines and Acid Gases………………….3 Facilitated Transport Membrane for Acid-gas Removal………………….2 CO2 (H2S)-Selective Membrane……….1 Membrane Synthesis and Characterization……………………………….3 CO2 Transport Properties…………………………………………………. Flue Gas CO2 Removal….2 CO2 Capture Experiments……………………………………………………….4 Results and Discussion………………………………………….1 Transport Properties of CO2-selective Membrane ……………………….2 CO2 Removal Capacity…………………………………………………….3 CO2 Capture Performance.1 Effect of Feed Inlet Flow Rate……………………………………….2 Effect of Sweep-to-Feed Ratio………………………………………. High-Pressure CO2 and H2S Removal from Natural Gas.3 Results and Discussion………………………………………………………….1 Free-Standing Membrane………………………………………………….1 Effect of Feed Pressure on CO2 Transport Properties……………….2 Effect of Temperature on CO2 Transport Properties…………….3 Effect of Permeate Pressure on CO2 Transport Properties………….2 Thin-Film Composite Membrane………………………………………….1 Effect of Membrane Thickness on CO2 Transport Properties….2 Effect of Temperature on CO2 and H2S Transport Properties………. Other CO2-Selective Membranes…………………………………………………….2 Hybrid Facilitated Transport Membrane………………………….1 Synthesis of Hybrid Membrane………………………………………….2 Results and Discussion………………………………………………….3 Segmented Polyimide Copolymer…………………………………………….1 Membrane Synthesis and Testing……………………………………….2 Results and Discussion………………………………………………….
Modeling of CO2-selective WGS membrane reactor for fuel cells.3 Experimental Study of CO2-Selective WGS Membrane Reactor …………….4 Results and Discussion…………………………………………………………130 6.1 Autothermal Reforming Syngas………………………………………….2 Effect of CO2/H2 Selectivity……………………………………….3 Effect of CO2 Permeability…………………………………………133 6.4 Effect of Sweep-to-Feed Ratio…………………………………….5 Effect of Inlet Feed Temperature………………………………….6 Effect of Inlet Sweep Temperature…………………………………135 6.7 Effect of Feed-Side Pressure……………………………………….8 Effect of Inlet Feed CO Concentration…………………………….9 Effect of Catalyst Activity………………………………………….2 Steam Reforming Syngas…………………………………………………138 6.2 Effect of CO2/H2 Selectivity……………………………………….3 Effect of CO2 Permeability…………………………………………140 6.4 Effect of Sweep-to-Feed Ratio…………………………………….5 Effect of Inlet Feed Temperature………………………………….6 Effect of Inlet Sweep Temperature…………………………………142 6.7 Effect of Feed-Side Pressure……………………………………….8 Effect of Feed Inlet CO Concentration…………………………….9 Effect of Catalyst Activity………………………………………….3 Membrane Reactor Results………………………………………………. Conclusions and recommendations………………………………………………….1 CO2 (H2S)-selective polymeric membranes and applications………………….2 Recommendations for Future Work…………………………………………….182 Bibliography……………………………………………………………………………185 xii LIST OF TABLES Table Page 2.1 Carbamate stability constants for different amines at 40oC by carbon-13 NMR (Sartori and Savage, 1983) ………………………………………………………30 3.1 The operating parameters for the CO2 capture experiments…………………….1 Diols as the option of soft segment…………………………………………….2 The testing results of copolymer membrane……………………………………109 6.1 The compositions of autothermal reforming syngas and steam reforming syngas………………………………………………………………………….147 xiii LIST OF FIGURES Figure Page 2.1 Facilitated transport mechanism…………………………………………………31 2.2 Synthesis of the crosslinked PVA with formaldehyde.3 Chemical structures of (a) free polyallylamine and (b) AIBA-K……………….4 Schematic of the gas permeation unit……………………………………………34 2.5 Scanning electron microscopic picture of the membrane synthesized………………35 2.6 CO2 permeability vs.7 CO2/H2 selectivity vs.8 CO2/N2 selectivity vs.9 H2S and CO2 permeability vs.10 H2S/H2 and CO2/H2 selectivity vs.11 H2S removal capacity with the circular gas permeation cell (24.1 Schematic of the hollow-fiber membrane module……………………………….2 Schematic of gas separation with the CO2-selective membrane…………………….3 Exit dry CO2 concentration in the retentate vs. feed flow rate………………….4 Permeate CO2 dry concentration and CO2 recovery vs. feed flow rate………….5 Permeate CO2 dry concentration and CO2 recovery vs.
sweep-to-feed molar ratio………………….6 CO2 concentration (wet) profiles along the length of membrane module…….1 Schematic of gas separation with the CO2 (H2S)-selective membrane………….2 CO2 permeability and CO2/CH4 selectivity vs. feed pressure at 106oC………….3 CO2 permeability and CO2/CH4 selectivity vs. feed pressure at 116oC………….4 CO2 permeability and CO2/CH4 selectivity vs. temperature at 150 psia feed pressure………………………………………………………………………….5 CO2 permeability and CO2/CH4 selectivity vs.
temperature at 500 psia feed pressure………………………………………………………………………….6 CO2 permeability and CO2/CH4 selectivity vs. permeate pressure at 106oC and 500 psia feed pressure……………………………………………………………85 4.7 CO2 permeability and CO2/CH4 selectivity vs. permeate pressure at 111oC and 500 psia feed pressure……………………………………………………………86 4.8 CO2 permeability and CO2/CH4 selectivity vs. permeate pressure at 116oC and 500 psia feed pressure……………………………………………………………87 4.9 CO2 permeance and CO2/CH4 selectivity vs.
membrane thickness at 116oC and 150 psia feed pressure……………………………………………………………88 4.10 Total mass transfer resistance, Rt, versus membrane thickness………………….11 CO2/CH4 and H2S/CH4 selectivities versus operating temperature…………….12 CO2 and H2S permeances versus operating temperature……………………….13 Schematic of the phase inversion process with the delayed demixing (■ denotes the top of the liquid film, ● denotes the bottom of the liquid film, and red lines denote the composition path along the liquid film thickness) ………………….14 The weight reduction of the membrane during the air-drying (23oC, casting gap setting = 10 mil) …………………………………………………………………93 4.15 The preliminary data from the asymmetric membranes via the phase inversion process (106oC and 150 psia feed pressure) …………………………………….1 CO2/H2 selectivity of PVA membrane and hybrid PVA membrane……………110 5.2 CO2/N2 selectivity of PVA membrane and hybrid PVA membrane……………111 5.3 CO2 permeability of PVA membrane and hybrid PVA membrane.4 The thermogravimetric curves for the hybrid PVA membrane and the PVA membrane……………………………………….5 Reaction steps in the synthesis of 2 PMDA/ 1 PEA 2000/ 1 MDA….6 FTIR spectra of copolymer, 2 PMDA / 1 PEA 2000 / 1 MDA, after imidization…………………………………………………………………….1 Schematic of water-gas-shift hollow-fiber membrane reactor………………….2 Cross-section schematic of the water-gas-shift membrane reactor…………….3 Feed-side CO and CO2 mole fraction profiles along the length of membrane reactor for autothermal reforming syngas………………………………………150 6.4 Feed-side H2 mole fraction profiles along the length of membrane reactor for autothermal reforming syngas………………………………………………….5 Feed-side and sweep-side temperature profiles along the length of membrane reactor for autothermal reforming syngas………………………………………152 6.6 The effects of CO2/H2 selectivity on feed-side exit CO concentration and H2 recovery for autothermal reforming syngas…………………………………….7 The effect of CO2 permeability on required membrane area for autothermal reforming syngas………………………………………….8 The effects of sweep-to-feed ratio on feed-side exit CO concentration and H2 recovery for autothermal reforming syngas……………………………….9 The effect of inlet feed temperature on required membrane area for autothermal reforming syngas………………………………………………………….10 Feed-side temperature profiles along the length of membrane reactor for autothermal reforming syngas with different inlet feed temperatures……….11 The effect of inlet sweep temperature on required membrane area for autothermal reforming syngas……………………………………………………………….12 Feed-side temperature profiles along the length of membrane reactor for autothermal reforming syngas with different inlet sweep temperatures……….13 The effect of feed-side pressure on required membrane area for autothermal reforming syngas……………………………………………………………….14 Feed-side CO mole fraction profiles along the length of membrane reactor for autothermal reforming syngas with different inlet feed CO temperatures…….15 The effect of catalyst activity on required membrane area for autothermal reforming syngas……………………………………………………………….16 Feed-side CO and CO2 mole fraction profiles along the length of membrane reactor for steam reforming syngas…………………………………………….17 Feed-side H2 mole fraction profiles along the length of membrane reactor for steam reforming syngas……………………………………………………….18 Feed-side and sweep-side temperature profiles along the length of membrane reactor for steam reforming syngas…………………………………………….19 The effects of CO2/H2 selectivity on feed-side exit CO concentration and H2 recovery for steam reforming syngas………………………………………….20 The effect of CO2 permeability on required membrane area for steam reforming syngas………………………………………………………………………….21 The effects of sweep-to-feed ratio on feed-side exit CO concentration and H2 recovery for steam reforming syngas………………………………………….22 The effect of inlet feed temperature on required membrane area for steam reforming syngas……………………………………………………………….23 Feed-side temperature profiles along the length of membrane reactor for steam reforming syngas with different inlet feed temperatures……………………….24 The effect of inlet sweep temperature on required membrane area for steam reforming syngas……………………………………………………………….25 Feed-side temperature profiles along the length of membrane reactor for steam reforming syngas with different inlet sweep temperatures…………………….26 The effect of feed-side pressure on required membrane area for steam reforming syngas………………………………………………………………………….