Reactive Absorption of CO2 in Single and Blended Amine Systems Hammad Majeed Chemical Engineering Submission date: July 2013 Supervisor: Hallvard Fjøsne Svendsen, IKP Norwegian University of Science and Technology Department of Chemical Engineering Dedicated To Nature , it’s Creator & My Parents ACKNOWLEDGMENT In the Name of Almighty ALLAH to whom my all praises are. He is the one who gave me courage to perform this work. I am pleased to pay credit to Chemical Engineering department of NTNU for offering each possible facility in making my effort triumphant. I would like to express my profound gratitude to my supervisor, Professor Hallvard F. Svendsen for giving me the opportunity to join in the CO capture research group whose brainwave, 2 motivation and stimulating suggestions enabled me to complete this thesis work. Thanks a lot to my co-advisors Hanna Knuutila & Juliana G. Monteiro for their exceptional guidance and for readily sharing their profound expertise in the most delightful manner. I would also like to pay gratitude to Ardi Hartono for his un parallel suggestions in every field, whether it’s an experimental work or modeling. His quest for performing high quality research was inspirational to me. I hereby declare that this is an independent work according to the exam regulations of Norwegian University of Science and Technology. NTNU, Trondheim 15.07.2013 Author ABSTRACT Global warming scenario is pretty grim and is a well-known worldwide concern, most likely caused by increasing concentrations of CO and other greenhouse gases in the earth’s atmosphere 2 due to human activities. CO absorption in amine-based absorbents is an established and proven 2 technology. Unfortunately, this process is still very energy intensive and has high capital costs. The main theme of this work is to characterize new generation solvents; kinetics of CO 2 absorption in single and blended amine system is a part of this mission. Kinetics of CO in aqueous MAPA system with concentration of 1/2/3/4/5 M and aqueous 2 blended system of MAPA+DEEA with variant concentrations were measured at a temperature range of 298.15-338.15 K. The kinetic experiments for both systems were performed in string of disc contactor. Results for rate constants were interpreted in terms of single step termolecular mechanism proposed by “Crooks et al., 1989” for the reaction of CO with amine because of its 2 less number of parameters. In addition to this work, the physical properties like density from 293.15-353.15 K and viscosity with in span of 293.15-333.15 K were also measured to determine the physio chemical parameters. The solubility of N O in aqueous MAPA system and aqueous blended systems were 2 performed to estimate the solubility of CO in MAPA and blended (MAPA+DEEA) solutions at 2 temperature range of 298.15-338.15K. Densities of systems were measured in Anton Paar DMA 4500M density meter while viscosities were estimated in Physica MCR 100 rheometer and solubility experiments were done in stirred jacketed glass vessel. Simple model based on temperature and concentration was applied on excel sheet in order to calculate the density, solubility and viscosity. The absorption flux of CO in MAPA and blended 2 systems, Henry’s constants, over all mass transfer coefficients and second order rate constants were determined for each case and compared these with the citied data available in order to judge the behavior and performance of current systems. TABLE OF CONTENTS 1. Introduction.................................................................................................................................... 1 1.1 Why to Capture CO .............................................................................................................. 1 2 1.2 Carbon Capture and Storage (CCS) ...................................................................................... 2 1.3 CO Capture Technologies .................................................................................................... 2 2 1.3.1 Pre-Combustion CO Capture ........................................................................................ 2 2 1.3.2 Post Combustion CO Capture ....................................................................................... 3 2 1.3.3 Oxy-Fuel Combustion .................................................................................................... 3 1.4 Separation Methodologies ..................................................................................................... 5 1.4.1 Chemical Absorption ...................................................................................................... 5 1.4.2 Physical Absorption ........................................................................................................ 5 1.4.3 Physical Adsorption ........................................................................................................ 6 1.4.4 Membrane Technologies ................................................................................................ 6 1.4.5 Cryogenic Separation ..................................................................................................... 6 1.5 CO Transport and Storage .................................................................................................... 7 2 1.6 Unfolding Concepts and Research for CO Capture ............................................................ 8 2 1.7 Interest & Span of Current Work .......................................................................................... 8 2 Back ground ................................................................................................................................. 11 2.1 Physiochemical Properties ................................................................................................... 11 2.1.1 Solubility ....................................................................................................................... 11 2.1.2 Density ........................................................................................................................... 12 2.1.3 Diffusivity ..................................................................................................................... 13 2.1.4 Viscosity ........................................................................................................................ 13 2.2 Kinetics of Alkanolamines ................................................................................................... 14 2.2.1 Zwitterion Mechanism.................................................................................................. 14 2.2.2 Termolecular Mechanism ............................................................................................. 17 2.3 Mass Transfer with a Chemical Reaction ........................................................................... 18 2.3.1 Two Film Theory .......................................................................................................... 19 2.3.2 Surface Renewal Model ............................................................................................... 21 2.3.3 Film-Penetration Theory .............................................................................................. 22 2.4 Chemical Equilibrium .......................................................................................................... 23 2.4.1 Chemical Equilibria in (CO -Water- DEEA System) ................................................ 23 2 2.4.2 Chemical Equilibria in (CO -Water- MAPA System) .............................................. 24 2 2.5 Reaction Regime................................................................................................................... 24 2.5.1 Slow Reaction Regime ................................................................................................. 25 2.5.2 Fast Reaction Regime ................................................................................................... 25 2.5.3 Instantaneous Reaction Regime ................................................................................... 25 2.5.4 Slow Reaction Regime ................................................................................................. 25 2.5.5 Fast Reaction Regime ................................................................................................... 26 2.5.6 Instantaneous Reaction Regime ................................................................................... 26 2.6 Gas Side Resistance.............................................................................................................. 27 2.6.1 Liquid Phase Control .................................................................................................... 27 2.6.2 Gas Phase Control ......................................................................................................... 28 2.7 Liquid Film Mass Transfer Coefficient............................................................................... 28 2.8 Gas Film Mass Transfer Coefficient ................................................................................... 28 2.9 Kinetic Rate Constant........................................................................................................... 29 2.9.1 Rate Constant for Zwitterion Mechanism ................................................................... 29 2.9.2 Rate Constant for Termolecular Mechanism .............................................................. 30 2.10 Activity Based Rate Constant .......................................................................................... 30 3 Materials and Experimental Setup ............................................................................................. 32 3.1 Chemicals for CO and Amine Analyses ............................................................................ 33 2 3.1.1 Standard Solutions ........................................................................................................ 33 3.1.2 Filters ............................................................................................................................. 33 3.2 Experimental Setup .............................................................................................................. 33 3.2.1 String of Discs Contactor Apparatus (SDC) ............................................................... 33 3.2.2 Solubility Assessment................................................................................................... 37 3.2.3 Density Measurement ................................................................................................... 39 3.2.4 Viscosity Determination ............................................................................................... 40 3.3 Process of Analyzing ............................................................................................................ 42 3.3.1 CO Analyses of Samples............................................................................................. 42 2 3.3.2 Amine Analysis of Samples ......................................................................................... 43 3.4 Accuracy / Uncertainty ........................................................................................................ 43 4 Results & Discussions ................................................................................................................. 45 4.1 Density Evaluations: ............................................................................................................ 45 4.1.1 Density Comparison (Current Work & Literature)..................................................... 48 4.2 Viscosity Evaluation ............................................................................................................ 50 4.2.1 Viscosity Comparison (Current Work & Literature) .................................................. 53 4.3 Solubility Determination ...................................................................................................... 55 4.3.1 Solubility Comparison (Current Work & Literature) ................................................. 58 4.4 Kinetic Evaluation of Aqueous MAPA System ................................................................. 59 4.4.1 Absorption Flux ............................................................................................................ 59 4.4.2 Overall Mass Transfer Coefficient .............................................................................. 62 4.4.3 Observed Kinetic Rate Constant .................................................................................. 63 4.4.4 Second Order Kinetic Rate Constant ........................................................................... 66 4.4.5 Comparison of Modeled and Experimental (Absorption Flux and K ) ..................... 68 2 4.5 Kinetic Evaluation of Aqueous Blended System ............................................................... 70 4.5.1 Absorption Flux ............................................................................................................ 70 4.5.2 Overall Mass Transfer Coefficient .............................................................................. 72 4.5.3 Observed Kinetic Rate Constant .................................................................................. 73 4.5.4 Second Order Kinetic Rate Constant ........................................................................... 75 4.6 Comparison of Aqueous MAPA System & Aqueous Blended System (Current Work) . 76 5 Conclusions & Proposed Future Work………………………………………………………82 6 References……………………………………………………………………………………83 7 Appendix……………………………………………………………………………………..89