Continuous Bunsen reaction and simultaneous separation using a counter-current flow reactor for the sulfur–iodine hydrogen production process

Abstract

The sulfur–iodine (SI) process, which consists of three chemical reactions of the Bunsen reaction, a H2SO4 decomposition and a HI decomposition, is an important potential method for hydrogen production among thermochemical water splitting methods. For steady-state operation of the SI process, it is very important to provide information on the composition of each phase that passes from the Bunsen reaction section to the following H2SO4 and HI decomposition sections. In this study, the Bunsen reaction was carried out using a counter-current flow reactor, the Bunsen reaction and product separation steps were shown capable of being performed simultaneously, and the composition variation of each phase discharged at the top and bottom of reactor was investigated. The process variables were the SO2 feed rate, temperature, I2/H2O molar ratio. As a result of constant reactant feed and continuous product discharge operation, it was found that the composition remained constant after 120 min of reaction time, indicating steady-state operation. The phase separation characteristics of the Bunsen reaction were minimally affected by the SO2 feed rate. As the amount of I2 introduced increased with increasing temperature, the volume of the H2SO4 phase discharged from the upper phase was unchanged, while that of the HIx phase discharged from the lower phase increased proportionally. The average molar composition of the H2SO4 phase (H2SO4/H2O/HI) obtained at a typical operation condition (353 K, I2/H2O molar ratio of 0.406) was 1/5.30–5.39/0.02–0.04, and the composition of the HIx phase (HI/I2/H2O/H2SO4) was 1/2.81–3.09/5.67–6.40/0.04–0.06. These results could be used for the design and operation of H2SO4 and HI decomposition sections of the SI process.