Occurrence of the Bunsen side reaction in the sulfur-iodine thermochemical cycle for hydrogen production

This study aimed to establish a closed-cycle operation technology with high thermal efficiency in the thermochemical sulfur-iodine cycle for large-scale hydrogen production.A series of experimental studies were performed to investigate the occurrence of side reactions in both the H2SO4 and HI x phases from the H2SO4/HI/I2/H2O quaternary system within a constant temperature range of 323-363 K.The effects of iodine content,water content and reaction temperature on the side reactions were evaluated.The results showed that an increase in the reaction temperature promoted the side reactions.However,they were prevented as the iodine or water content increased.The occurrence of side reactions was faster in kinetics and more intense in the H2SO4 phase than in the HI x phase.The sulfur or hydrogen sulfide formation reaction or the reverse Bunsen reaction was validated under certain conditions.

Using a simulation software to perform energy and exergy analyses of the sulfur-iodine thermochemical process

The objective of this work is to demonstrate the utilization of the power of simulation tools to perform an exergy analysis of a process.Exergy analysis,being a new and useful thermodynamics tool,will be applied to one of the newest research fields in hydrogen production.One of the many advantages of computer simulation is elimination of the need to construct a pilot plant.Presently,extensive research is underway to come up with the production and use of clean fuels.The research entails performing pilot studies and proof of concept experiments using validated models.The research is further extended to various analyses such as safety,economic sustainability and energy efficiency of the processes involved.The production of hydrogen through thermochemical water splitting processes is one of the newest technologies and is expected to compete with the existing technologies.Among a wide range of thermochemical cycles,the sulfur-iodine(SI)thermochemical cycle process has been proposed as a promising technology for the production of hydrogen.In this research,we demonstrate how a commercial simulator can be used to perform an energy and exergy analysis of the SI water splitting process.Using a commercial simulator,a process flowsheet is developed based on research findings presented by other authors and an energy-exergy analysis is carried out on the process.The method of energy–exergy analysis used in this presentation indicates that an energy and exergy efficiency of 17%and 24%can be attained,respectively,in the conceptual design of the SI cycle.

A review of recent researches on Bunsen reaction for hydrogen production via S–I water and H2S splitting cycles

The Bunsen reaction is the center reaction for both the sulfur–iodine water splitting cycle for hydrogen production and the novel hydrogen sulfide splitting cycle for hydrogen and sulfuric acid production from the sulfur-containing gases.This paper reviews the research progress of the Bunsen reaction in recent 10–15 years.Researches were initially focused on the optimization of the operating conditions of the conventional Bunsen reaction requiring excessive water and iodine to improve the products separation efficiency and to avoid the side reactions and iodine vapor deposition.Alternative methods including electrochemical methods,precipitation methods,and non-aqueous solvent methods had their respective advantages,but still faced challenges.In development of the technology of H2S splitting cycle,dissolving iodine in toluene solvent could render the Bunsen reaction to occur with the flowable I2 stream at ambient temperature such that the side reactions and iodine vaporization can be avoided and the corrosion hazard lessened.It also prevented the Bunsen reaction from using excessive iodine and water.The products from the Bunsen reaction including HI,H2SO4,H2O,and toluene could be directly electrolyzed.