Journal of Membrane Science 342 (2009) 269–278 Contents lists available at ScienceDirect Journal of Membrane Science journal homepage: www.elsevier.com/locate/memsci Mathematical modeling for the simultaneous absorption of CO 2 and H 2 S using MEA in hollow fiber membrane contactors Rami Faiz, M. Al-Marzouqi ∗ Chemical and Petroleum Engineering Department, UAE University, P.O. Box 17555, Al-Ain, United Arab Emirates article info Article history: Received 7 April 2009 Received in revised form 23 June 2009 Accepted 26 June 2009 Available online 5 July 2009 Keywords: Membrane contactors Simultaneous absorption Carbon dioxide Hydrogen sulfide Monoethanol amine (MEA) abstract A comprehensive two-dimensional mathematical model was developed for the simultaneous transport of carbon dioxide and hydrogen sulfide through hollow fiber membrane (HFM) contactors while using monoethanol amine (MEA) as the chemical solvent. The model considered non-wetting and partial- wetting conditions where the gas mixture and the solvent fill the membrane pores for countercurrent gas–liquid flow arrangement. Axial and radial diffusion were considered inside the fiber, through the membrane, and within the shell. The model was validated for physical and chemical absorption of CO 2 using water and MEA, respectively. The model results were in excellent agreement for the physi- cal absorption while considering non-wetting conditions. However, for chemical absorption the model showed excellent agreement with the experimental data while considering 10% wetting for polypropylene (PP) when 0.005 M MEA was used, and 50% wetting for polyvinyllidene fluoride (PVDF) when 2 M MEA was used. The effect of MEA concentrations, gas and liquid velocities were studied on the simultaneous removal of CO 2 and H 2 S. The % removal of CO 2 increased while increasing the MEA concentration. As for H 2 S, low concentration of MEA was efficient in complete removal. The % removal of CO 2 decreased while increasing gas velocity, whereas, H 2 S % removal did not change with increasing gas velocity when oper- ating at low gas velocity. However, the effect is more pronounced while operating at high gas velocities. Both CO 2 and H 2 S % removal was increased with increasing the liquid velocity. CO 2 % removal increased slightly, while H 2 S % removal increased substantially while operating at high gas velocity. © 2009 Elsevier B.V. All rights reserved. 1. Introduction Global warming and climate changes are believed to be caused by the rise of the greenhouse gases emissions, because of the global expansion of industrial activities over the past three decades [1]. Carbon dioxide is representing about 80% of greenhouse gases. It is reported that half of the CO 2 emissions are produced by indus- try and power plants using fossil fuels [2]. These emissions create the need for low energy-consumption, and efficient technologies for the capture and removal of CO 2 from gas mixtures produced by industrial sources. Another important gas produced in these indus- trial and domestic processes is Hydrogen Sulfide. H 2 S is a highly toxic and corrosive gas and is considered as one of the major sources of the environmental problems such as acid rains. Usually natu- ral gas refinery streams contain H 2 S and CO 2 as major impurities. Therefore, in order to utilize these fuels for chemical processing or energy generation, H 2 S and CO 2 must be removed. ∗ Corresponding author. Tel.: +971 3 762 1698; fax: +971 3 762 4262. E-mail addresses: remil@uaeu.ac.ae (R. Faiz), mhhassan@uaeu.ac.ae (M. Al-Marzouqi). Both H 2 S and CO 2 are acidic in nature and are similar in many physical and chemical aspects. Hence the processes used for the removal of CO 2 in gas treating processes also absorb H 2 S. The most common processes for removal of these acid gases are an absorp- tion into a solvent using conventional gas–liquid contactors such as packed or plate absorption towers. Simultaneous absorption of H 2 S and CO 2 using packed towers has been extensively studied, both experimentally and theoretically [3]. Using alkaline solution as the absorption medium, H 2 S selectivity was reported to be in the range of 10–30 [4]. However, these conventional chemical absorption pro- cesses for the removal of H 2 S and CO 2 suffer many drawbacks such as flooding, foaming, entraining, channeling, and high capital and operating costs. Therefore, many researchers have looked for new technologies to enhance the efficiency of these processes. Hollow fiber membrane (HFM) contactors attracted the attention of many researchers as a new technology for gas separation [5–10]. Membrane contactors are devices that allow two fluids to come into direct contact with each other, for the purpose of mass transfer without dispersion of one phase into the other. In the membrane contactor, the gas mixture flows in one side of a hydrophobic micro- porous membrane while the liquid absorbent flows in the other side. A gas–liquid interface will be formed at the pores opening adjacent to the liquid when the membrane pores are not wetted 0376-7388/$ – see front matter © 2009 Elsevier B.V. All rights reserved. doi:10.1016/j.memsci.2009.06.050