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Experimental Studies on CO2 Capture Using Absorbent in a Polypropylene Hollow Fiber Membrane Contactor
Mälardalen University, School of Sustainable Development of Society and Technology.
2011 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

In recent years, membrane gas absorption technology has been considered as one of the promising alternatives to conventional techniques for CO2 capture due to its favorable mass transfer performance. As a hybrid approach of chemical absorption and membrane separation, it exhibits a number of advantages, such as operational flexibility, compact structure, high surface-area-to-volume ratio, linear scale up, modularity and predictable performance. One of the main challenges of membrane gas absorption technology is the membrane wetting by absorbent over prolonged operating time, which may significantly decrease the mass transfer coefficients of the membrane module.

In this thesis, the experimental was set up to investigate the dependency of CO2 removal efficiency and mass transfer rate on various operating parameters, such as the gas and liquid flow rates, absorbent type and concentration and volume fraction CO2 at the feed gas inlet. In addition, the simultaneous removal of SO2 and CO2 was investigated to evaluate the feasibility of simultaneous desulphurization and decarbonization in the same membrane contactor. During 14 days of continuous operation, it was observed that the CO2 mass transfer rate decreased significantly following the operating time, which was attributed to partial membrane wetting.

To better understand the wetting mechanism of membrane pores during their prolonged contact with absorbents, immersion experiments for up to 90 days were carried out. Various membrane characterization methods were used to illustrate the wetting process before and after the membrane fibers were exposed to the absorbents. The characterization results showed that the absorbent molecules diffused into the polypropylene polymer during the contact with the membrane, resulting in the swelling of the membrane. In addition, the effects of operating parameters such as immersion time and absorbent type on the membrane wetting were investigated in detail. Finally, based on the analysis results, methods to smooth the membrane wetting were discussed. It was suggested that improving the hydrophobicity of polypropylene membrane by surface modification may be an effective way to improve the long-term operating performance of membrane contactors. Therefore, the polypropylene hollow fibers were modified by depositing a thin superhydrophobic coating on the membrane surface to improve their hydrophobicity. The mixture of cyclohexanone and methylethyl ketone was considered as the best non-solvent to achieve the fiber surface with good homogeneity and acceptably high hydrophobicity. In the long-period operation, the modified membrane contactor exhibited more stable and efficient performance than the untreated one. Hence, surface treatment provides a feasibility of improving the system stability for CO2 capture from the view of long-term operation.

Abstract [sv]

En av de tekniker som under senare framhållits som ett lovande alternativ till konventionell CO2-avskiljning är membran-gas-absorptionstekniken på grund av god prestanda vad gäller masstransport. Det blandade angreppssättet med både kemisk absorption och membranseparation har en rad fördelar, såsom driftflexibilitet, kompakt konstruktion, högt yt-volymsförhållande, linjär uppskalning, modularitet och förutsägbar prestanda. En av de viktigaste utmaningarna för membran-gas-absorptionstekniken är vätningen av membranet med absorbenten under långa drifttider, vilket väsentligt kan minska membranmodulens masstransportkoefficienter. 

I avhandlingen har en rad olika driftparametrars påverkan på CO2-reningsgraden och massöverföringshastigheten undersökts. Driftparametrar inkluderar gas- och vätskeflöden, typ av absorbent och koncentration och volymfraktion av CO2 vid gasinloppet. Avskiljning av SO2 och CO2 har dessutom undersökts för att utvärdera möjligheten att samtidigt, i samma membranenhet, avlägsna svavel och kol. Under 14 dagars kontinuerlig drift konstaterades det att massöverföringshastigheten för CO2 minskade avsevärt med drifttiden, vilket hänfördes till partiell vätning av membranet.  

För att bättre förstå mekanismerna för vätning av membranporer under långvarig kontakt med absorbenter genomfördes doppningsexperiment i upp till 90 dagar. Olika metoder för karakterisering av membran användes för att illustrera vätningsprocessen före och efter det att membranfibrerna exponerades för absorbenterna. Resultaten av karakteriseringen visade att absorbentmolekylerna spreds in i polypropenpolymeren under kontakten med membranet, vilket ledde till att membranet svällde. Dessutom undersöktes effekterna av driftsparametrar såsom nedsänkningstid och typ av absorbent i detalj. Slutligen, på grundval av analysresultaten, diskuterades metoder för att underlätta vätningen av membran. Att förbättra polypropylenmembranets hydrofobicitet genom modifiering av ytan föreslogs kunna vara ett effektivt sätt att förbättra den långsiktiga driftprestandan för membranenheter. Därför modifierades de ihåliga fibrerna av polyproylen med ett tunt lager av en superhydrofob beläggning på membranets yta för att förbättra hydrofobiciteten. En blandning av cyklohexanon och metyletylketon ansågs vara det bästa icke-lösningsmedlet för att få en fiber yta med god homogenitet och acceptabelt hög hydrofobicitet. Under lång driftperiod, uppvisade den modifierade membranenheten stabilare och effektivare prestanda än den obehandlade. Därför erbjuder ytbehandling en möjlighet till att förbättra systemets stabilitet för CO2-avskiljning när det gäller långsiktig drift.

Place, publisher, year, edition, pages
Västerås: Mälardalen University , 2011.
Series
Mälardalen University Press Dissertations, ISSN 1651-4238 ; 102
Keyword [en]
CO2 capture; Simultaneous removal of CO2 and SO2; Hollow fiber membrane contactor; Membrane gas absorption; Partial wetting; Surface modification
Keyword [sv]
CO2-avskiljning, samtidig avskiljning av CO2 och SO2, ihålig fiber, membran, gas absorption, vätning, ytmodifiering
National Category
Engineering and Technology
Research subject
Energy- and Environmental Engineering
Identifiers
URN: urn:nbn:se:mdh:diva-12320ISBN: 978-91-7485-023-9OAI: oai:DiVA.org:mdh-12320DiVA: diva2:419112
Public defence
2011-06-17, Lambda, Mälardalens högskola, Västerås, 10:00 (English)
Opponent
Supervisors
Projects
VR-SIDA Swedish Research Links Programme
Available from: 2011-05-27 Created: 2011-05-25 Last updated: 2014-01-22Bibliographically approved
List of papers
1. Experimental study on PP membrane modification and performance evaluation for CO2 absorption in hollow fiber membrane contactors
Open this publication in new window or tab >>Experimental study on PP membrane modification and performance evaluation for CO2 absorption in hollow fiber membrane contactors
2010 (English)In: The Second International Conference on Applied Energy (ICAE2010), 2010Conference paper (Refereed)
Abstract [en]

The membrane wetting by amine absorbents is a big concern and may result in performance deterioration of membrane gas absorption technology for CO2 post-combustion capture. In this paper, the polypropylene membrane was modified by depositing a rough layer on the membrane surface so as to improve the membrane non-wettability. Characterization results showed that the contact angle increases dramatically from 122˚ to 162˚ by the modification, thereby improving the hydrophobicity of the membrane. The modified membrane characteristics were also studied by the correlation of scanning electron microscope and atomic force microscopy results. In addition, CO2 absorption in the polypropylene hollow fiber membrane contactors with and without surface modification was investigated in a continuous experiment for 20 days using an aqueous MEA solution as the absorbent. The long-term system operation results showed that the modified PP hollow fiber membrane contactor is feasible for CO2 capture from the flue gas of large-scale power plants.

Keyword
Carbon dioxide capture; Hollow fiber membrane contactors; Partial wetting; Surface modification;
Research subject
Energy- and Environmental Engineering
Identifiers
urn:nbn:se:mdh:diva-9615 (URN)
Conference
21-23 April, 2010, Singapore
Projects
Swedish Research Links Programme
Available from: 2010-05-24 Created: 2010-05-24 Last updated: 2013-07-30Bibliographically approved
2. CO2 capture by the absorption process in the membrane contactors
Open this publication in new window or tab >>CO2 capture by the absorption process in the membrane contactors
2009 (English)In: 6th Vienna International Conference on Mathematical Modeling, MATHMOD 2009, 2009Conference paper (Refereed)
Abstract [en]

Post combustion CO2 capture is corresponding to the most widely applicable option in terms of industrial sectors and is compatible to a retrofit strategy. In addition to the conventional chemical absorption process, membrane gas absorption is considered as one of the promising alternatives to conventional techniques for the CO2 separation from the flue gas of fossil fuels combustion. As a hybrid approach of chemical absorption and membrane separation, it may offer a number of important features, e.g., economical viability due to its larger interfacial area, no flooding at high flow rates, no foaming and channeling, linear scale-up with predictable performance. This paper is to describe and present the state-of-the-art of the R&D efforts on membrane contactors focused on the microporous hallow fiber structure. The operating principles, liquid absorbents selection, influence of membrane wetting phenomenon, membrane materials and module types have been intensively reviewed. Model parameters including economic performance has been evaluated with comparison of other technologies. Technical obstacles of applying membrane contactors in CO2 capture process have also been discussed. The knowledge and application gaps have been examined and identified, thus providing a recommendation for the future studies.

Keyword
CO2 capture and storage; carbon dioxide; hollow fiber membrane; membrane contactors; numerical modeling
National Category
Engineering and Technology
Research subject
Energy- and Environmental Engineering
Identifiers
urn:nbn:se:mdh:diva-9611 (URN)
Conference
MATHMOD 2009, Austria, February 11 - 13, 2009
Projects
Swedish Research Links Programme
Available from: 2010-05-24 Created: 2010-05-24 Last updated: 2014-01-14Bibliographically approved
3. Fabrication and characterization of superhydrophobic polypropylene hollow fiber membranes for carbon dioxide absorption
Open this publication in new window or tab >>Fabrication and characterization of superhydrophobic polypropylene hollow fiber membranes for carbon dioxide absorption
Show others...
2012 (English)In: Applied Energy, ISSN 0306-2619, E-ISSN 1872-9118, Vol. 90, no 1, 167-174 p.Article in journal (Refereed) Published
Abstract [en]

The membrane wetting by amine absorbents results in performance deterioration of membrane gas absorption system for CO2 post-combustion capture. To solve this problem, in this study, the polypropylene membrane fiber was modified by depositing a rough layer on the surface to improve its hydrophobicity. Weighing the coating homogeneity, hydrophobicity and modification process efficiency, the mixture of cyclohexanone and MEK system was considered as the best non-solvent. The contact angle increased dramatically from 122_ to 158_ by the modification, thereby obtaining superhydrophobic membrane surface. The membrane–absorbent interaction results demonstrated that the modification treatment effectively enhanced the stability and maintained the superhydrophobicity of fibers contacting with the absorbent. In addition, continuous CO2 absorption experiments for up to 20 days were carried out in untreated and modified polypropylene hollow fiber membrane contactors, using 1 mol L_1 MEA solution as the absorbent. The long-term system operation results indicated that, even though additional mass transfer resistance was introduced by the surface coating, the modified polypropylene hollow fiber

membrane contactor was still technically feasible for CO2 capture from the power stations.

Keyword
CO2 capture; Hollow fiber membrane contactors;Partial wetting;Hydrophobic modification
National Category
Engineering and Technology
Research subject
Energy- and Environmental Engineering
Identifiers
urn:nbn:se:mdh:diva-12318 (URN)10.1016/j.apenergy.2010.12.038 (DOI)000297426100026 ()2-s2.0-80055031249 (ScopusID)
Projects
VR-SIDA
Available from: 2011-05-25 Created: 2011-05-25 Last updated: 2014-06-16Bibliographically approved
4. Experimental Studies on Simultaneous Removal of CO2 and SO2 in a Polypropylene Hollow Fiber Membrane Contactor
Open this publication in new window or tab >>Experimental Studies on Simultaneous Removal of CO2 and SO2 in a Polypropylene Hollow Fiber Membrane Contactor
Show others...
2012 (English)In: Applied Energy, ISSN 0306-2619, E-ISSN 1872-9118, Vol. 97, 283-288 p.Article in journal (Refereed) Published
Abstract [en]

Membrane gas absorption technology is a promising alternative to conventional technologies for the mitigation of acid gases. In this study, simultaneous removal of SO2 and CO2 from coal-fired flue gas was studied in a polypropylene hollow fiber membrane contactor using aqueous monoethanolamine as the absorbent. The influences of liquid and gas flow rates on the simultaneous absorption performance of CO2 and SO2 were investigated. The experimental results indicated that the membrane contactor could eliminate these two sour gases simultaneously and effectively. Absorption of SO2 and CO2 was enhanced by the increase in liquid flow rate and decrease in gas flow rate. It was observed that a small amount of SO2 in the flue gas had a slight influence on the absorption of CO2. In addition, the membrane contactor was continuously operated for two weeks to evaluate its duration performance. The results showed that the CO2 mass transfer rate was decreased significantly with the operating time due to partial wetting of membrane pores. After 14 days of continuous operation, the CO2 mass transfer rate of the wetted membrane contactor was decreased by 41% but could be retrieved to 86% of the fresh one by increasing the gas phase pressure.

Keyword
Simultaneous absorption; CO2 removal; SO2 removal; Membrane gas absorption; Partial wetting
National Category
Engineering and Technology
Research subject
Energy- and Environmental Engineering
Identifiers
urn:nbn:se:mdh:diva-12319 (URN)10.1016/j.apenergy.2012.01.034 (DOI)000307196000033 ()2-s2.0-84862305631 (ScopusID)
Conference
3rd International Conference on Applied Energy (ICAE), MAY 16-18, 2011, Perugia, ITALY
Projects
VR-SIDA Swedish Research Links Programme
Available from: 2011-05-25 Created: 2011-05-25 Last updated: 2014-01-10Bibliographically approved
5. Experimental investigation on CO2 absorption using absorbent in hollow fiber membrane contactor
Open this publication in new window or tab >>Experimental investigation on CO2 absorption using absorbent in hollow fiber membrane contactor
2008 (English)In: International Scientific Conference on "Green Energy management and IT", Stockholm, March 12-13, 2008, 2008Conference paper (Refereed)
Identifiers
urn:nbn:se:mdh:diva-1146 (URN)
Available from: 2010-10-04 Created: 2008-10-03 Last updated: 2013-12-04Bibliographically approved
6. Wetting of polypropylene hollow fiber membrane contactors
Open this publication in new window or tab >>Wetting of polypropylene hollow fiber membrane contactors
Show others...
2010 (English)In: Journal of Membrane Science, ISSN 0376-7388, Vol. 362, no 1-2, 444-452 p.Article in journal (Refereed) Published
Abstract [en]

The membrane wetting by the absorbent leads to the increase of mass transfer resistance and deterioration of CO2 absorption performance during membrane gas absorption process. In this paper, polypropylene (PP) fibers were immersed in monoethanolamine (MEA), methyldiethanolamine (MDEA) and deionized (DI) water, respectively, assuming that the immersed PP fibers would undergo similar exposure conditions as those used in hollow fiber membrane contactor. The wetting evolution of PP fibers was investigated as a function of immersion time. The characterization results confirmed that the absorbent molecules diffused into the PP polymer during the exposure process, resulting in the swelling of the membrane. The absorption-swelling wetting mechanism was proposed to explain what happened during the wetting process. A 30.8° reduction in the contact angle was observed, indicating that the membrane surface hydrophobicity decreased significantly following the immersion time. Experimental results showed that the membrane surface morphology and surface roughness suffered significant and complicated changes after being immersed in the absorbents for a certain period. It was found that the absorbent with higher surface tension is in favor of fewer changes of the membrane surface morphologies. Based on the experimental results, improving the membrane surface hydrophobicity was suggested as an effective way to overcome the wetting problem.

Keyword
Wetting; Hollow fiber membrane contactors; Polypropylene; Surface morphologies; CO2 capture
National Category
Engineering and Technology
Research subject
Energy- and Environmental Engineering
Identifiers
urn:nbn:se:mdh:diva-10361 (URN)10.1016/j.memsci.2010.06.067 (DOI)000281571100049 ()2-s2.0-77955665036 (ScopusID)
Projects
Swedish Research Links Programme
Available from: 2013-06-17 Created: 2010-10-04 Last updated: 2014-06-19Bibliographically approved
7. INFLUENCE OF MEA AND MDEA SOLUTIONS ON SURFACE MORPHOLOGY OF MICROPOROUS POLYPROPYLENE MEMBRANES
Open this publication in new window or tab >>INFLUENCE OF MEA AND MDEA SOLUTIONS ON SURFACE MORPHOLOGY OF MICROPOROUS POLYPROPYLENE MEMBRANES
Show others...
2009 (English)In: The First International Conference on Applied Energy (ICAE09), 2009Conference paper (Refereed)
Abstract [en]

Membrane has a potential to improve the CO2 capture process. In this paper, experimentswere carried out to investigate the impact of amine absorbents on membrane surfaceproperties with polypropylene (PP) fibers immersed in monoethanolamine (MEA) andmethyldiethanolamine (MDEA) aqueous solutions with and without CO2 loading. The surfacemorphological changes of the membrane were examined by using scanning electronmicroscopy (SEM). The experimental results showed that the fibers immersed in the aqueoussolutions without CO2 loading underwent significant deformation than those with CO2 loading,which is mostly linked to the decrease of absorbent concentration with the reaction betweenCO2 and aqueous solutions. It was also found that the morphological changes of membraneimmersed in MDEA were severer than that in MEA due to the lower surface tension of theformer.

Research subject
Energy- and Environmental Engineering
Identifiers
urn:nbn:se:mdh:diva-7598 (URN)
Conference
The First International Conference on Applied Energy (ICAE09)
Available from: 2010-10-04 Created: 2009-11-29 Last updated: 2013-12-04Bibliographically approved
8. CO2 capture by the absorption process in membrane contactors
Open this publication in new window or tab >>CO2 capture by the absorption process in membrane contactors
Show others...
2009 (English)In: The First International Conference on Applied Energy (ICAE09), 2009Conference paper (Refereed)
Abstract [en]

Membrane has a potential to improve the CO2 capture process. In this paper, experimentswere carried out to investigate the impact of amine absorbents on membrane surfaceproperties with polypropylene (PP) fibers immersed in monoethanolamine (MEA) andmethyldiethanolamine (MDEA) aqueous solutions with and without CO2 loading. The surfacemorphological changes of the membrane were examined by using scanning electronmicroscopy (SEM). The experimental results showed that the fibers immersed in the aqueoussolutions without CO2 loading underwent significant deformation than those with CO2 loading,which is mostly linked to the decrease of absorbent concentration with the reaction betweenCO2 and aqueous solutions. It was also found that the morphological changes of membraneimmersed in MDEA were severer than that in MEA due to the lower surface tension of theformer.

Keyword
Carbon dioxide capture; Hollow fiber membrane contactors; Membrane
Research subject
Energy- and Environmental Engineering
Identifiers
urn:nbn:se:mdh:diva-8234 (URN)
Conference
The First International Conference on Applied Energy (ICAE09)
Available from: 2009-11-29 Created: 2009-11-29 Last updated: 2013-12-04Bibliographically approved

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