EVALUATION OF AN IRON-CHLORINE THERMOCHEMICAL CYCLE FOR HYDROGEN PRODUCTION

C.A.CANAVESIO; H.E.P.NASSINI; A. E. BOHÉ

INTERNATIONAL JOURNAL OF HYDROGEN ENERGY

PERGAMON-ELSEVIER SCIENCE LTD

Año: 2015 vol. 40 p. 8620 - 8632

0360-3199

In this paper, a theoretical and experimental study on an iron-chlorine thermochemical cyclefor hydrogen production is presented. The study was addressed to confirm the occurrence of thethermochemical reactions originally proposed and to investigate the influence of kinetic parametersfor improving the overall performance of this cycle. Firstly, a thermodynamic analysis was done fordetermining whether this iron-chlorine thermochemical cycle is attractive for hydrogen production atreaction temperatures below 1223 K, in terms of both energy efficiency and yield of desired products.Following, proof-of-concept experiments using a batch reactor were performed at different reactiontemperatures, pressures and holding times. Experimental results showed that the reactiontemperature is expected to have a small effect for increasing the hydrogen production, while anincrease of the system pressure was observed to raise markedly the conversion degree achieved. Basedon experimental results, it was possible to confirm the reaction pathway of thermochemical reactionsoriginally proposed, to identify the rate determining step of the overall process, and to explain thebeneficial effect of increasing the system pressure on the hydrogen yield. Finally, a modified cycle isproposed for increasing its overall energy efficiency, by lowering the reaction temperature of twothermochemical reactions from 1198 K to 923 K in order to avoid the phase change of FeCl2 that meltsat 950 K. Comparative calculations of enthalpy balance and external heat and work requirements forthe original and modified cycles showed that the limiting energy efficiency could be theoreticallyincreased from the range 24-28% to 32-37%.