Membrane gas–solvent contactor trials of CO 2 absorption from syngas Colin A. Scholes, Michael Simioni, Abdul Qader, Geoff W. Stevens, Sandra E. Kentish ⇑ Cooperative Research Centre for Greenhouse Gas Technologies (CO2CRC), Department of Chemical and Biomolecular Engineering, The University of Melbourne, VIC 3010, Australia highlights " Membrane gas absorption tested with PP and PTFE membranes using carbonate and amine solvents. " Solvent in shell side led to higher overall mass transfer coefficients than solvent in lumen. " Pilot scale trials with syngas showed reduced performance due to membrane wetting. article info Article history: Received 9 January 2012 Received in revised form 10 April 2012 Accepted 10 April 2012 Available online 27 April 2012 Keywords: Membrane Contactor Polypropylene Potassium carbonate Monoethanolamine Polytetrafluoroethylene Syngas abstract Membrane gas–solvent contactors incorporate the advantages of both solvent absorption and membrane gas separation technologies. Here, gas–solvent contactors are applied to the separation of carbon dioxide from syngas in a coal fired pilot plant. Two contactors, based on polypropylene (PP) and polytetrafluoro- ethylene (PTFE), are trialed with two solvents, 30 wt.% monoethanolamine (MEA) and 30 wt.% potassium carbonate (K 2 CO 3 ) solutions. To validate performance, results were also obtained with a mixture of 10% CO 2 in N 2 in the laboratory. All contactor–solvent systems tested in the laboratory behaved in accordance with membrane contactor models with only minor pore wetting observed. Mass transfer coefficients were improved when solvent flowed on the shell side of the contactor due to increased turbulence and reduced pore wetting relative to the lumen side. In contrast, for the pilot plant trials with syngas, only the PP–K 2 CO 3 and PTFE–MEA systems provided mass transfer coefficients similar to those deter- mined in the laboratory. For the PTFE–K 2 CO 3 system, additional pore wetting resulted in reduced overall mass transfer coefficients. The PTFE–MEA system retained the best overall mass transfer performance, due to reduced pore wetting and greater reaction enhancement. Ó 2012 Elsevier B.V. All rights reserved. 1. Introduction The demonstration of carbon capture technologies is becoming increasingly important, as solutions to reduce anthropogenic car- bon emissions are sought. Two viable carbon capture technologies are membrane gas separation and reversible solvent absorption [1], both of which are currently commercialized in natural gas pro- cessing. Hybrid membrane–solvent systems, known as membrane gas absorption, seek to exploit the advantages of both membrane gas separation and solvent absorption technologies [2]. The process involves the transfer of CO 2 from the process gas through a non- selective porous hollow-fiber membrane where it is chemically ab- sorbed into a solvent. This takes advantage of the highly selective nature of solvent technology, while incorporating the benefits of membrane technology in terms of reduced equipment size, the modular nature of the equipment, and flexibility in orientation [3]. A membrane contactor can achieve much greater mass transfer area per unit volume than conventional solvent absorption column technology. Reed et al. [4] indicate that 500–600 m 2 /m 3 can be achieved in a membrane contactor compared to 100–250 m 2 /m 3 in a traditional column. Similarly, Falk-Pedersen et al. [3] indicate that the reduced specific area of a membrane contactor allows for a 65–75% reduction in weight and size compared to conventional towers. Further, the membrane acts to physically separate the liquid and gas flows, which eliminates foaming and reduces liquid channeling, two major operating issues in solvent absorption columns [2]. There are three main strategies for carbon capture from com- bustion processes, post-combustion capture, pre-combustion cap- ture and oxy-fired combustion [1]. In pre-combustion capture, fossil fuels are reformed into synthesis gas (syngas) comprised mainly of hydrogen and carbon monoxide [5]. More hydrogen is produced by further converting CO through the water gas-shift reaction, resulting in high pressure CO 2 and H 2 [6]. Separation of these two components allows for the storage of CO 2 , while H 2 can be used for a number of purposes, such as power generation [1]. Pre-combustion processes can be further classified into those that use oxygen-blown gasification and those that use an air- blown gasifier [7]. In the former case, the shifted syngas is a simple 1385-8947/$ - see front matter Ó 2012 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.cej.2012.04.034 ⇑ Corresponding author. Tel.: +61 3 8344 6682; fax: +61 3 8344 4153. E-mail address: sandraek@unimelb.edu.au (S.E. Kentish). Chemical Engineering Journal 195–196 (2012) 188–197 Contents lists available at SciVerse ScienceDirect Chemical Engineering Journal journal homepage: www.elsevier.com/locate/cej