In this study, removal of hydrogen sulfide (H2S) and carbon dioxide (CO2) 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 H2S 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 H2S 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 H2S removal overweighed to structured packings. The coexistence of CO2 and H2S has been shown to increase the sodium hydroxide (NaOH) consumption along the scrubber column thereby decreasing the H2S removal efficiency at higher H2S 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 3s were seemed to be closer to the optimum point. (C) 2014 The Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.