For integrated operation of the sulfur-iodine (SI) hydrogen production process, a HI. solution consisting of HI, I-2 and H2O could be recycled as a reactant to the Bunsen reaction section from the HI decomposition section. In this study, characteristics of the Bunsen reaction using the HI. solution in a co-current flow mode were investigated experimentally. In particular, we studied the effects of the operating variables (feed rates of reactants, H2O and I-2 feed concentrations, temperature and volume of reaction zone) on the characteristics of the Bunsen reaction under steady-state conditions. Increasing the H2O feed concentration and decreasing the I-2 feed concentration improved the extent of the Bunsen reaction. When increasing the temperature, the purity of the Bunsen products improved, but the SO2 conversion decreased. Characteristics of the Bunsen reaction were not affected by the variation in the volume of reaction zone. We concluded that SO2/HI/I-2/H2O feed molar ratio controlled in the ranges of 1/1.8-2.0/3.9-4.1/14.8-15.6 was advantageous to achieve high SO2 conversion and improve separation performance of the Bunsen products at 333 K. (C) 2016 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.