A Dissertation entitled Membrane Process Design for Post-Combustion Carbon Dioxide Capture by Norfamila Che Mat Submitted to the Graduate Faculty as partial fulfillment of the requirements for the Doctor of Philosophy Degree in Chemical Engineering ________________________________________ Dr. Glenn Lipscomb, Committee Chair ________________________________________ Dr. Maria Coleman, Committee Member ________________________________________ Dr. Yakov Lapitsky, Committee Member ________________________________________ Dr. Constance Schall, Committee Member ________________________________________ Dr. Matthew Franchetti, Committee Member ________________________________________ Dr. Amanda Bryant-Friedrich, Dean College of Graduate Studies The University of Toledo December 2016 Copyright 2016, Norfamila Che Mat This document is copyrighted material. Under copyright law, no parts of this document may be reproduced without the expressed permission of the author. An Abstract of Membrane Process Design for Post-Combustion Carbon Dioxide Capture by Norfamila Che Mat Submitted to the Graduate Faculty as partial fulfillment of the requirements for the Doctor of Philosophy Degree in Chemical Engineering The University of Toledo December 2016 Concerns over the effects of anthropogenic carbon dioxide (CO2) emissions from fossil-fuel electric power plants has led to significant efforts in the development of processes for CO2 capture from flue gas. Options under consideration include absorption, adsorption, membrane, and hybrid processes. The US Department of Energy (DOE) has set goals of 90% CO2 capture at 95% purity followed by compression to 140 bar for transport and storage. Ideally, the Levelized Cost of Electricity (LCOE) would increase by no more than 35%. Because of the relatively low CO2 concentration in post-combustion flue gas, most of the reported process configurations for membrane systems have sought to generate affordable CO2 partial pressure driving forces for permeation. Membrane Technology and Research, Inc. (MTR) proposed the use of an air feed sweep system to increase the CO2 concentration in flue gas. This process utilizes a two-stage membrane process in which the feed air to the furnace sweeps the flue gas in the second stage to iii reduce the flow of CO2 in the effluent to 10% of that leaving the furnace. Such a design significantly reduces capture costs but leads to a detrimental reduction in the oxygen concentration of the feed air to the boiler. In this dissertation, the economic viability of combined cryogenic-membrane separation is evaluated. The work incorporates the tradeoff between CO2/N2 selectivity and CO2 permeability that exists when considering the broad range of potential membrane materials. Of particular interest is the use of lower selectivity, higher permeability materials such as polydimethylsiloxane (PDMS). Additional enriching stages are required in a membrane-cryogenic air feed sweep configuration to enable use of these materials and achieve the 90% CO2 recovery and 95% purity targets. The higher CO2 permeance of PDMS significantly reduces the total module membrane area requirement and associated capital cost (CAPEX). However, the lower selectivity increases the parasitic plant load required to produce the desired CO2 purity due the need for an additional membrane stage and the associated recycle loops; this increases operating cost (OPEX). Multistage membrane-cryogenic air feed sweep configurations are optimized using the Robeson upper bound relation to relate membrane permeability to selectivity. Membrane selectivity is varied over a broad range encompassing the values considered by MTR. Permeability is varied with selectivity according to the variation anticipated by the upper bound of the Robeson plot for CO2 and N2. Membrane permeance is calculated assuming membranes can be fabricated with an effective thickness of 0.1 micron. Additionally, the two stages may utilize different membrane materials. The feed and iv permeate pressures also are varied over ranges encompassing the values proposed by MTR. The optimization space of membrane properties and operating conditions is scanned globally to determine the process design that minimizes LCOE. The oxygen concentration to the boiler is evaluated during the optimization process and can be used to constrain viable alternatives. The results indicate a fairly broad range of membrane properties can yield comparable LCOE near the minimum. The optimal operating pressure range is somewhat narrower. The minimum allowable oxygen concentration can constrain viable designs significantly and is critical to process economics. Membrane separation system shows a rapid response as the incoming flow flue gas flow rate changes due to the small time constant value. High pressure ratio and low CO2/N2 shows the fastest response due to the smaller residence time. Considering the fixed membrane area, compressor and vacuum power, step changes of incoming flue gas flow rate results in the variation effect of feed compression pressure and also vacuum permeate pressure. This leads to selectivity dependent changes in permeate flow that affect CO2 recovery. v Acknowledgements I would like to extend my sincerest thanks and appreciation my advisor Dr. Glenn Lipscomb for his support, patience, guidance and mentorship over the past 4 years. Thank you for instilling in me an interest in this area; and always challenging me to think in ways I had never imagined possible. Special thanks to Dr. Coleman, Dr. Lapitsky, Dr. Schall and Dr. Franchetti for agreeing to serve on my dissertation committee. My heartfelt thanks to my parents, family and partner(s) in crime for the never ending support, prayers and encouragement throughout my studies. Thank you for all the joy and laughter that has helped me a lot throughout tough times. Last but not least, financial support from Ministry of Higher Education Malaysia (PhD Fellowship) and University Malaysia Sarawak (study leave) is gratefully acknowledged. vi Table of Contents Abstract ........................................................................................................................................ iii Acknowledgements ....................................................................................................................... vi Table of Contents ......................................................................................................................... vii List of Figures ............................................................................................................................... xii List of Tables ............................................................................................................................. xviii List of Abbreviations .................................................................................................................. xix List of Symbols ............................................................................................................................ xxi 1. Introduction ................................................................................................................................ 1 1.1 Membrane Separation Processes for Post-Combustion ......................................................... 1 1.2 Membrane Air Feed Sweep Configurations ........................................................................... 3 1.3 Research Objectives ............................................................................................................... 7 1.4 Research Significance ............................................................................................................ 9 1.5 Structure of Dissertation ...................................................................................................... 12 2. Literature Review .................................................................................................................... 15 2.1 CO2 Emissions from Electricity Power Generation Sources ............................................... 15 2.2 CO2 Emissions Mitigations Options from Electricity Power Generation ............................ 17 2.3 Carbon Capture and Storage (CCS) ..................................................................................... 17 2.3.1 Pre-Combustion ............................................................................................................ 18 vii 2.3.2 Oxyfuel Combustions .................................................................................................... 18 2.3.3 Post-Combustion ........................................................................................................... 18 2.4 Carbon Capture and Storage (CCS) Economic Evaluations ................................................ 19 2.4.1 Levelized Cost of Electricity (LCOE) ............................................................................ 20 2.4.2 Cost of CO2 Avoided ..................................................................................................... 22 2.4.3 Cost of CO2 Captured ................................................................................................... 23 2.5 Membrane Process Design for Post-Combustions Applications ......................................... 23 2.5.1 Hollow Fiber Membrane Module ................................................................................. 23 2.5.2 Gas Permeation Model ................................................................................................