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Experimental and Theoretical Investigation into Alternative Versions of the Bunsen Reaction

Michela Lanchi, Giampaolo Caputo, Claudio Felici, Alberto Giaconia, and Salvatore Sau. ENEA, via Anguillarese, 301, Rome, 00060, Italy

The Sulphur-Iodine thermochemical process is currently considered one of the most promising cycle for large scale hydrogen production from water. Although it has been investigated for several years by different research groups (GA and JAERI above all), still there are substantial discrepancies about its thermal efficiency, which is evaluated in the range 0,33-0,42%. The last theoretical studies identify the separation between water and sulphuric acid on one hand, and water, hydriodic acid and iodine on the other hand as the most energy consuming step of the cycle. For this reason Bunsen reaction can be considered the key step of the whole cycle, as its operative conditions affect the separation and purification of the two liquid phases generated. Therefore the improvement of the thermal efficiency of the cycle requires the optimization of the Bunsen section operative conditions, in order to obtain two phases as concentrated and pure as possible, reducing the possibility of side reactions. So far the experimental work carried out at ENEA (the Italian National Agency for New Technology, Energy and the Environment) on the Bunsen section confirms the results published by JAERI and doesn't leave space for relevant improvements regarding the two liquid phases separation and purification. An other possible route to increase the thermal efficiency of the cycle is to modify the Bunsen reaction in terms of reagents, solvents and operative conditions. The focus of the present work is the assessment of an alternative version of the Sulphur-Iodine cycle, in which the conventional Bunsen reaction is replaced by different reactive systems, characterized by the presence of iodine, metallic sulphates, condensed sulphur dioxide and water. Experimental measurements and theoretical analysis have been carried out in order to evaluate the feasibility of the conceived alternative process and the resulting thermal efficiency has been estimated.