The effects of SO2 flow rate, SO2 mole fraction, iodine content and water content on the Bunsen reaction were experimentally studied for the thermochemical iodine–sulfur cycle for hydrogen production. One multistage reaction mechanism on the Bunsen reaction has been hypothesized, considering the kinetic characteristics. The appearance of a liquid–liquid equilibrium (LLE) phase separation was in the range of 20–40 min in the apparatus we chose. An increase in iodine content and a decrease in water content improved LLE separation characteristics to the H2SO4 phase and HIx phase. The H2S formation side reaction easily occurred with the increase in water content and decrease in iodine content. The optimal operating condition that the inlet SO2 mole fraction exceeds 0.12 coupled with initial I2/H2O molar ratio exceeding 0.284 has been proposed based on the experimental results, for the criteria of improving the separation characteristics and preventing side reactions.
Ke Zhang,Xu Zhao,Sihan Chen,Liping Chang,Jiancheng Wang,Weiren Bao,Hui Wang
In chemical cycles to produce hydrogen , the H 2 S splitting cycle and the sulfur-iodine (S I) water splitting cycle both share the Bunsen reaction and HI decomposition. Therefore, they have to overcome the same challenges in the technology development, one of them being the complex and difficult separations of the mixed hydroiodic acid and sulfuric acid solution after the Bunsen reaction. To avoid the separations, this paper studies the electrolysis of the HI/H 2 SO 4 /H 2 O/toluene mixture, focusing on the electrochemical characterization of the Pt electrode by using linear sweep voltammetry (LSV) and cyclic voltammetry (CV). The results show that hydrogen is identified from the gas generated from the cathode in electrolysis. Iodide oxidation is the main reaction in the anode chamber and no significant side reactions are observed. Iodine deposition on the anode surface increases the resistance to iodide diffusion to the anode. However, it can be mitigated by adding toluene in or applying stirring to the anolyte HI/H 2 SO 4 solution. The Pt cathode and sulfuric acid catholyte also work stably.
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