Thermodynamic Properties of CO2 Mixtures and Their Applications in Advanced Power Cycles with CO2 Capture Processes Hailong Li Energy Processes Department of Chemical Engineering and Technology Royal Institute of Technology Stockholm, Sweden KTH, Royal Institute of Technology School of Chemical Science and Engineering Department of Chemical Engineering and Technology Division of Energy Processes SE-100 44 Stockholm Sweden Copyright © Hailong Li, 2008 All rights reserved TRITA-CHE Report 2008:58 ISSN 1654-1081 ISBN 978-91-7415-091-9 Hope it is something… Abstract: The thermodynamic properties of CO2 mixtures are essential for the design and operation of CO2 capture and storage (CCS) systems. A better understanding of the thermodynamic properties of CO2 mixtures could provide a scientific basis to define a proper guideline of CO2 purity and impure components for the CCS processes according to technical, safety, and environmental requirements. However, the available accurate experimental data cannot cover the entire operation conditions of the CCS processes. In order to overcome the shortage of experimental data, theoretical modelling and estimation are used as a supplemental approach. In this thesis, the available experimental data on the thermodynamic properties of CO2 mixtures were first collected; their applicability and gaps for theoretical model verification and calibration were also determined according to the required thermodynamic properties and operation conditions of CCS. Then, in order to provide recommendations concerning calculation methods for the engineering design of CCS, a total of eight equations of state (EOS) were evaluated for the calculations concerning vapour liquid equilibrium (VLE) and volume of CO2 mixtures, including N2, O2, SO2, Ar, H2S, and CH4. With the identified equations of state, the preliminary assessment of the impact of impurity was further conducted regarding the thermodynamic properties of CO2 mixtures and the different processes involved in the CCS system. Results show that the increment of the mole fraction of non-condensable gases would make purification, compression, and condensation more difficult. Comparatively, N2 can be separated more easily from the CO2 mixtures than O2 and Ar. Moreover, a lower CO2 recovery rate is expected for the physical separation of CO2/N2 under the same separation conditions. In addition, the evaluations of the acceptable concentration of non-condensable impurities show that the transport conditions in vessels are more sensitive to the non-condensable impurities, thus, requiring very low concentration of non-condensable impurities in order to avoid two-phase problems. Meanwhile, the performances of evaporative gas turbine integrated with different CO2 capture technologies were investigated from both technical and economical aspects. It is concluded that the evaporative gas turbine (EvGT) cycle with chemical absorption capture has a smaller penalty on electrical efficiency, but a lower CO2 capture ratio than the EvGT cycle with O2/CO2 recycle combustion capture. Therefore, although EvGT + chemical absorption has a higher annual cost, it has a lower cost of electricity because of its higher efficiency. However, considering its lower CO2 capture ratio, EvGT + chemical absorption has a higher cost to capture 1 ton CO2. In addition, the efficiency of EvGT + chemical absorption can be increased by optimizing Water/Air ratio, increasing the operating pressure of stripper, and adding a flue gas condenser condensing out the excessive water. Language: English. Keywords: thermodynamic property, vapour liquid equilibrium, volume, equation of state, interaction parameter, CO2 mixtures, evaporative gas turbine, chemical absorption, oxy-fuel combustion, cost evaluation, CO2 capture and storage I II Table of Contents Abstract .............................................................................................................................. I Table of Contents............................................................................................................ III List of Tables .................................................................................................................... V List of Figures................................................................................................................ VII List of Papers and Technical Reports ............................................................................ IX Acronyms ........................................................................................................................XI 1 Introduction ...........................................................................................................- 1 - 1.1 Global Warming and CO2 Capture and Storage (CCS) .................................................. - 1 - 1.2 Problems and Challenges.................................................................................................. - 2 - 1.3 Objectives ........................................................................................................................ - 3 - 1.4 Methodology.....................................................................................................................- 3 - 1.5 Outline of the Thesis........................................................................................................ - 4 - Part I: Thermodynamic Properties of CO2 Mixtures ................................................... - 7 - 2 Method Evaluations for the Thermodynamic Property Calculations of CO2 Mixtures ........................................................................................................................- 7 - 2.1 Necessary Thermodynamic Properties and Potential Operation Conditions of CCS ........... - 7 - 2.2 Available Experimental Data and Gaps Regarding CO2 and CO2 Mixtures.................. - 9 - 2.3 Evaluation of Calculation Models on Thermodynamic Properties of CO2 Mixtures.........- 11 - 2.4 Discussions....................................................................................................................- 19 - 3 Impact of Impurity on Thermodynamic Properties of CO2 Mixtures and Different Processes Involved in the CCS Systems ......................................................................- 21 - 3.1 Impact of Impurity on Thermodynamic Properties of CO2 Mixtures................................- 22 - 3.2 Impact of Impurity on the Different Processes Involved in the CCS Systems.....................- 25 - 3.3 Discussions....................................................................................................................- 32 - Part II: Evaporative Gas Turbine Cycles Integrated with CO2 Capture.....................- 35 - 4 Evaporative Gas Turbine Cycles Integrated with Different CO2 Capture Technologies................................................................................................................- 35 - 4.1 System Configurations....................................................................................................- 35 - 4.2 Thermodynamic Performances of Various Systems..........................................................- 38 - 4.3 Economic Evaluation on Various Systems.....................................................................- 43 - III 4.4 Investigation of EvGT Integrated with MEA Based Chemical Absorption Capture Regarding Electrical Efficiency.....................................................................................................................- 45 - 4.5 Discussions....................................................................................................................- 48 - 5 Conclusions...............................................................................................................- 51 - Appendix......................................................................................................................- 53 - References....................................................................................................................- 57 - Acknowledgements......................................................................................................- 63 - IV List of Tables Table 2.1 Major thermodynamic properties of CO2 mixtures required by the CCS system design and engineering evaluation ....................................................................................................... - 7 - Table 2.2 Estimated operation conditions (P and T) of the CCS processes.............................. - 8 - Table 2.3 Summary of the available experimental data for pure CO2 ....................................... - 10 - Table 2.4 Summary of the experimental data for binary CO2 mixtures.................................... - 10 - Table 2.5 Summary of TPxy ranges of the VLE experimental data for binary CO2 mixtures ........ .................................................................................................................................................... - 11 - Table 2.6 Summary of TPxy ranges of the volume experimental data for binary CO2 mixtures.... .................................................................................................................................................... - 11 - Table 2.7 Summary of studied cubic EOS for VLE calculations .............................................. - 15 - Table 2.8 Correlated kij for different binary CO2 mixtures based on VLE experimental data........ ...................................................................................................................................................