Please cite this article in press as: Üresin, E., et al., An experimental study for H 2 S and CO 2 removal via caustic scrubbing system. Process Safety and Environmental Protection (2014), http://dx.doi.org/10.1016/j.psep.2014.06.013 ARTICLE IN PRESS PSEP-462; No. of Pages 7 Process Safety and Environmental Protection x x x ( 2 0 1 4 ) xxx–xxx Contents lists available at ScienceDirect Process Safety and Environmental Protection journal h om ep age: www.elsevier.com/locate/ps ep An experimental study for H 2 S and CO 2 removal via caustic scrubbing system Ersin Üresin a,*,1 , Halil ˙ Ibrahim Sarac ¸ b , Alper Sarıo ˘ glan a , S ¸ iringül Ay a , Fehmi Akgün a a TÜB ˙ ITAK Marmara Research Center Energy Institute, P.O. Box 21, 41470 Gebze, Kocaeli, Turkey b Kocaeli University, Mechanical Engineering Department, Kocaeli, Turkey a b s t r a c t In this study, removal of hydrogen sulfide (H 2 S) and carbon dioxide (CO 2 ) from simulated syngas has been studied on one column scrubbing system. Gas flow rate as a measure of gas residence time and superficial gas velocity, gas composition, inlet H 2 S load, flow modes (countercurrent and cocurrent) and packing geometry were the parameters in the design and/or operation of an acid gas scrubber system. Better H 2 S scrubbing efficiencies have been obtained in countercurrent flow mode than that of cocurrent flow mode. When accordingly designed, static mixer with its superior performance on H 2 S removal overweighed to structured packings. The coexistence of CO 2 and H 2 S has been shown to increase the sodium hydroxide (NaOH) consumption along the scrubber column thereby decreasing the H 2 S removal efficiency at higher H 2 S loads. The gas residence time as changing with the gas velocity was found to be more dominant on acid gas removal efficiency than the effect of superficial gas velocity within the experimented range. A gas residence times of equal or above 3 s were seemed to be closer to the optimum point. © 2014 The Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved. Keywords: Gas clean up; Packed bed gas scrubbers; Hydrogen sulfide removal; CO 2 removal; NaOH; Static mixer 1. Introduction Particulate, ammonia (NH 3 ) and hydrogen sulfide (H 2 S) com- prise the main impurities of synthetic raw gas produced by coal gasification. Removal of these contaminants is an essen- tial step in coal and biomass gasification process to avoid its detrimental effects on materials and environment. Hydrogen sulfide and ammonia can cause corrosion in pipelines and thus limit plant lifetime. These are also a well-known cata- lyst poisoner. Therefore, utilization of gasification products either as a fuel for gas turbines, gas engines or fuel cells or as a syngas for Fischer–Tropsch fuel, ammonia or methanol pro- ductions requires an effective gas clean-up technology (Chen et al., 2001; Moussavi et al., 2008; Panza and Belgiorno, 2010). For the abatement of H 2 S and NH 3 , packed towers are widely used for chemical and physical scrubbing. The choice of the solution is critical in determining dissolution or chemical ∗ Corresponding author. Tel.: +90 262 677 27 80; fax: +90 262 641 23 09. E-mail address: ersin.uresin@tubitak.gov.tr (E. Üresin). 1 Present address. reaction rate of pollutant in the liquid. In physical scrub- bing, the pollutants in basic nature can be passivated by the acidic solutions and vica-versa. Currently, the processes of choice in the commercial integrated gasification com- bined cycle (IGCC) facilities for the removal of acid gases are both the chemical solvent acid gas removal processes based on aqueous methyldiethanolamine (MDEA) and the physi- cal solvent-based Selexol process which uses mixtures of dimethyl ethers and polyethylene glycol (Couvert et al., 2008; Turpin et al., 2008; Ohtsuka et al., 2009; Wang et al., 2004; Wallin and Olausson, 1993). Alkaline hypochlorite, hydrogen peroxide or caustic solu- tions are economicaly alternative solvents to be used in physical solvent-based processes and show good results for decades. Sodium hydroxide solution is a very effective, but non-regenerable absorbent for CO 2 and H 2 S. Therefore the use of caustic is usually limited to the removal of trace amounts of http://dx.doi.org/10.1016/j.psep.2014.06.013 0957-5820/© 2014 The Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.