Thermodynamic Analysis and Screening ILs/DESs-based Absorbents for CO Separation

234 Pages·2016·6.66 MB·English

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Thermodynamic Analysis and Screening
ILs/DESs-based Absorbents for CO
2
Separation
Yingying Zhang
Energy Engineering
Division of Energy Science
Department of Engineering Sciences & Mathematics
Luleå University of Technology
SE-971 87 Luleå, Sweden
Printed by Luleå University of Technology, Graphic Production 2016
ISSN 1402-1544
ISBN 978-91-7583-622-5 (print)
ISBN 978-91-7583-623-2 (pdf)
Luleå 2016
www.ltu.se
Abstract
CO separation plays an important role in both biofuel production, and CO capture and
2 2
storage (CCS) implementation to deal with global warming. The available CO separation
2
technologies are eitherenergy-intensiveorrequire large-scale operations, and it is crucial to
develop novel CO separation technology in order to optimize the energy uses and the
2
amountsof CO -absorbents/adsorbents.
2
Recently, ionic liquids (ILs) have been proposed as potential liquid absorbents for CO
2
separationwith remarkableproperties.Alot of ILshave been synthesized for this purpose.
The CO absorption capacity/selectivity and the energy use have been considered in
2
screening ILs, while the amounts of ILs needed have seldom been considered in the
screening process. Meanwhile, the high-cost, toxicity and poor biodegradability of the
conventional ILslimit theirapplicationsin large-scale.Deep eutectic solvents (DESs) have
emerged as a new type of ILs, and in particular, those based on choline salts (i.e.
choline-based DESs) show additional advantages in cost, environmental impact and
synthesis.Choline-based DESs have beensynthesizedand the research workrelatedto CO
2
separation with this series of DESs and their aqueous solutions has been carried out.
However, it is still unclear which absorbent can achieve a better performance for CO
2
separation.
The choice ofabsorbents for CO separationdepends ongas streams, and the performances
2
of absorbents for CO separation relate to the energy uses and the amounts of absorbents
2
needed. In this thesis work, four gas streams (i.e. flue gas and lime kiln gas from the
combustion of fossil-fuels, biogas from the anaerobic digestion of biomass as well as
bio-syngas from the gasification of biomass) with different temperature, pressure, CO
2
concentration andgaseous componentswere considered,and CO separationfrom four gas
2
streamswas analyzed thermodynamically based on Gibbs free energy change.The analysis
shows thatbiogas isthe CO stream with the lowest theoretical energy penalty.Therefore,
2
biogas was chosen as a specific CO stream for further evaluatingthe performancesof CO
2 2
absorbents.
In evaluation, the conventional ILs were first analyzed and screened for CO separation
2
i
from biogas with three options (i.e. option 1: the CO dissolution enthalpy and CO
2 2
working capacity, option 2:the energy use,and option 3:the energy useand the amount of
IL needed). The investigation shows that the screen of ILs is strongly related to the
operational condition and the screening criteria. In the option of “the energy use and the
amount of IL needed”, the operational condition was optimized based on the minimum
Gibbs free energy change, and the energy use and the amount of IL needed were considered
in screening. While in other screening options, the operational conditions were presumed
and the amounts of ILs needed were not considered. Therefore, the option of “the energy
use and the amount of IL needed” is more reasonable compared to the other two options.
The performancesof thesescreened conventional ILs werefurther compared with thoseof
the commercial CO absorbents. It shows that the conventional ILs are promising CO
2 2
absorbents due to lower energy uses or lower amounts of ILs needed combined with the
advantage of non-volatility.
The research work on choline-based DESs and their aqueous solutions for CO separation
2
wassurveyed and reviewed. Generally, the properties of choline-based DESs are similar to
those of conventional ILs. Considering the additional advantages of low-cost, non-toxicity
and biodegradability, choline-based DESs are more promising for CO separation.
2
However, due to the limited available research work,further studies need to be carried out
from experimental measurementsto modeldevelopments.
The performances of choline-based-DESs for CO separation from biogas were analyzed.
2
Based on the option of “the energy use and the amount of absorbent needed”, the
choline-based-DESs were screened and then compared with the conventional ILs and the
commercial CO absorbents. The comparisonresults show that the choline-based-DESs are
2
more promising for CO separation from biogasdue to the non-volatility,lowerenergy uses
2
or lower amounts of absorbents needed. In addition, CO separation from other CO
2 2
streamswas further investigated.It shows thatthe physical absorbentsare more suitable for
the CO streams with high CO concentration (i.e. biogas, lime kiln gas and bio-syngas),
2 2
while the chemical CO absorbents are more suitable for that with low CO concentration
2 2
and high temperature (i.e. flue gas). Considering the high amounts of physical absorbents,
further study needs to be carried out with techno-economic analysis.
ii
Appended publications
A. Zhang Y, Ji X, Lu X. Energy consumption analysis for CO separation from gas
2
mixtures, Applied Energy, 2014, 130: 237–243.
B. Xie Y, Zhang Y, Lu X, Ji X. Energy consumption analysis for CO separation using
2
imidazolium-based ionic liquids.Applied Energy. 2014,136:325-335.
C. Zhang Y, Ji X, Xie Y, Lu X.Screening of conventional ionic liquids for carbon dioxide
capture and separation,Applied Energy,2016,162:1160-1170.
D. Zhang Y, Ji X, Xie Y, Lu X. Thermodynamic analysis of CO separation with
2
conventional ionic liquids.Submittedto Applied Energy
E. Chen Y, Zhang Y, Yuan S, Ji X, Yang Z, Lu X. Thermodynamic study for the
absorbent of (2-hydroxyethyl)-trimethyl-ammonium(S)-2-pyrrolidinecarboxylic acid
salt + polyethylene glycol. Submittedto Journal of Chemical Engineering Data
F. Zhang Y, Ji X, Lu X. Choline-based deep eutectic solvents for CO separation: review
2
and thermodynamic analysis.Manuscript
Contributions of the author
A. Zhang was responsible for planning the work, carrying out the calculation and writing
paper together with co-authors.
B. Zhangcontributedtothe calculation of the energy consumption.
C. Zhang was responsible for planning the work, carrying out the calculation and writing
paper together with co-authors.
D. Zhang was responsible for planning the work, carrying out the calculation and writing
paper together with co-authors.
E. Zhang contributed to carrying out the thermodynamic analysis and the comparison of
different CO absorbents.
2
F. Zhang was responsible for planning the work, reviewing the choline-based DESs,
carrying out the calculationand writingpaper together with co-authors.
iii
Additional publications not included in this thesis
Article
1. Wu X, Lu L, Zhu Y, Zhang Y, Cao W, Ionic hydration of Na+inside carbon nanotubes
under electric fields, Fluid Phase Equilibria, 2013, 353:1-6.
2. Zhang Y, Lu X,Feng X, ShiY, Ji X.Properties and applications of choline-based deep
eutectic solvents.Progress in Chemistry, 2013,25(06): 881-892. (In Chinese)
3. Zhang Y, Ji X, Lu X. Application of choline-based deep eutectic solvents in CO
2
mitigation technology,CIESC Journal, 2014, 65(5), 1721-1728. (In Chinese)
4. Zhang Y, Ji X, Lu X. Properties and applications of choline chloride urea and choline
chloride glycerol.Science China: Chemistry,2014,44 (6): 927-941.(In Chinese)
Book chapter
1. Zhang Y, Ji X, Lu X. Choline-based deep eutectic solvents for mitigating carbon
dioxide emissions. In Novel Materials for Carbon Dioxide Mitigation Technology. Fan
Shi and Bryan Morreale, Eds. 2015, 87-116.
Conference proceeding
1. Zhang Y, Xie Y, Zhu Y, Lu X, Ji X, Energy consumption analysis for CO separation
2
from gas mixtures with liquid absorbents, Energy Procedia, 2014, 61: 2695-2698.
2. Ji X, Xie Y, Zhang Y, Lu X.CO capture/separation using choline chloride-based ionic
2
liquids, Proceeding of International Conference on Properties and Phase Equilibria for
Products andProcess Design. Argentina-Brazil, May, 2013.
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Content
Abstract...............................................................................................................................................i
Appended publications.....................................................................................................................iii
1 Introduction................................................................................................................................1
1.1 Background................................................................................................................................1
1.2 Performance evaluation.............................................................................................................2
1.3 Objectives and outline...............................................................................................................4
2 Theory and methodology...........................................................................................................5
2.1 Thermodynamic framework......................................................................................................5
2.2Thermodynamic analysis of CO separation process................................................................6
2
2.2.1 CO streams and separation................................................................................................6
2
2.2.2 CO separation....................................................................................................................8
2
2.2.2.1 (cid:507)G,(cid:507)G (cid:15)(cid:3)(cid:507)G (cid:68)(cid:81)(cid:71)(cid:3)(cid:507)G ’....................................................................................10
1 comp exp T
2.2.2.2 (cid:507)G (cid:68)(cid:81)(cid:71)(cid:3)(cid:507)G ..........................................................................................................10
abs des
2.2.2.3 (cid:507)G ............................................................................................................................13
T
2.2.3 Energy use........................................................................................................................14
2.2.4 Other thermodynamic properties......................................................................................15
2.3 Screening process....................................................................................................................16
2.3.1 Two-step screening process based on (cid:507)H (cid:68)(cid:81)(cid:71)(cid:3)(cid:507)m ...................................................16
dis CO2
2.3.2 Screening process based on Q ........................................................................................17
tot
2.3.3 Screening process based on Q and m ..........................................................................17
tot abs
3 Thermodynamic analysis of CO streams..............................................................................19
2
3.1 CO streams.............................................................................................................................19
2
3.2 Energy use analysis.................................................................................................................20
3.3 Sub-conclusion........................................................................................................................24
4 Screening of conventional ILs.................................................................................................25
4.1 Two-(cid:86)(cid:87)(cid:72)(cid:83)(cid:3)(cid:86)(cid:70)(cid:85)(cid:72)(cid:72)(cid:81)(cid:76)(cid:81)(cid:74)(cid:3)(cid:83)(cid:85)(cid:82)(cid:70)(cid:72)(cid:86)(cid:86)(cid:3)(cid:69)(cid:68)(cid:86)(cid:72)(cid:71)(cid:3)(cid:82)(cid:81)(cid:3)(cid:507)H (cid:68)(cid:81)(cid:71)(cid:3)(cid:507)m ..........................................................25
dis CO2
4.1.1 Preliminary screening.......................................................................................................25
4.1.2 Final screening..................................................................................................................26
4.1.3 Total Energy use...............................................................................................................27
4.2 Screening process based on Q ...............................................................................................28
tot
4.2.1 Pressure swing process.....................................................................................................29
4.2.2 Temperature swing process..............................................................................................29
4.2.3 Pressure and temperature swing process..........................................................................30
4.3 Screening process based on Q and m ..................................................................................31
tot IL
v
4.3.1 Performances of ILs.........................................................................................................31
4.3.2 Screening of ILs...............................................................................................................32
4.4 Comparisonsand discussions..................................................................................................32
4.5 Comparisons to commercial CO absorbents..........................................................................35
2
4.6 Sub-conclusion........................................................................................................................36
5 Screening of choline-based-DESs...........................................................................................37
5.1 Choline-based-DES survey.....................................................................................................37
5.1.1 Review on Choline-based DESs.......................................................................................37
5.1.2 Comparisons.....................................................................................................................38
5.2 Screening of choline-based-DESs based on Q and m ........................................................40
tot abs
5.2.1 Performancesof choline-based-DESs..............................................................................41
5.2.2 Screening of promising absorbents...................................................................................41
5.3 Comparisons to conventional ILs and commercial CO absorbents........................................42
2
5.4 Further discussion on CO streams..........................................................................................43
2
5.5 Sub-conclusion........................................................................................................................45
6 Conclusions...............................................................................................................................47
7 Future work..............................................................................................................................49
Acknowledgements..........................................................................................................................50
References........................................................................................................................................51
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