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Experimental Studies on Simultaneous Removal of CO2 and SO2 in a Polypropylene Hollow Fiber Membrane Contactor
Mälardalen University, School of Sustainable Development of Society and Technology.
E China Univ Sci & Technol, Shanghai.
E China Univ Sci & Technol, Shanghai.
Mälardalen University, School of Sustainable Development of Society and Technology.ORCID iD: 0000-0003-0300-0762
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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.

Place, publisher, year, edition, pages
2012. Vol. 97, 283-288 p.
Keyword [en]
Simultaneous absorption; CO2 removal; SO2 removal; Membrane gas absorption; Partial wetting
National Category
Engineering and Technology
Research subject
Energy- and Environmental Engineering
Identifiers
URN: urn:nbn:se:mdh:diva-12319DOI: 10.1016/j.apenergy.2012.01.034ISI: 000307196000033Scopus ID: 2-s2.0-84862305631OAI: oai:DiVA.org:mdh-12319DiVA: diva2:419095
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
In thesis
1. Experimental Studies on CO2 Capture Using Absorbent in a Polypropylene Hollow Fiber Membrane Contactor
Open this publication in new window or tab >>Experimental Studies on CO2 Capture Using Absorbent in a Polypropylene Hollow Fiber Membrane Contactor
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
CO2 capture; Simultaneous removal of CO2 and SO2; Hollow fiber membrane contactor; Membrane gas absorption; Partial wetting; Surface modification, 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:nbn:se:mdh:diva-12320 (URN)978-91-7485-023-9 (ISBN)
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

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