THERMO-CHEMICAL CYCLES APPLIED TO NUCLEAR HYDROGEN PRODUCTION IN ARGENTINA

C. CANAVESIO; M. BOSCO; NASSINI H.E.; A.E. BOHÉ

Praga

Workshop; Meeting Report of the Technical Meeting/Workshop on Non-Electric Applications of Nuclear Energy; 2011

International Atomic Energy Agency (IAEA)

In the present framework of worldwide reevaluation of nuclear energy, the hydrogen (H2) production using nuclear energy is receiving a great attention, since the demand of H2 is rapidly increasing as a result of decreased availability of light crude oils that do not require extra H2 for conversion to gasoline, with a corresponding increased use of heavy crude oils that require massive amounts of H2 for conversion to gasoline. Furthermore, if the cost goals for automotive fuel cells are reached, the transportation sector may be also fueled by H2 in the near future, in which case the H2 consumption is expected to grow one of two orders of magnitude over a period of several decades. Argentina has declared of national interest the development of technologies needed for the progressive introduction of H2 as a clean fuel and energy carrier that can be used to meet increasing residential, commercial, and industrial demands. Many research projects are currently underway at CNEA for achieving this goal: use of high temperature nuclear reactors as primary energy source, H2 production through coal gasification and thermo-chemical cycles, ultra purification methods, development of efficient ternary alloys for H2 storage, use of H2-methane hybrid fuel for public transportation, fuel cells development, and so on. Thermo-chemical cycles use a series of high-temperature chemical reactions for the decomposition of water into oxygen (O2) and H2, and they are expected to get and overall efficiency of about 50%. Even though over 200 thermo-chemical cycles have been identified for the water splitting, very few of them have progressed beyond theoretical calculations to experimental demonstrations. Metallic chlorides cycles decompose water into O2 and H2 through intermediate metal and chlorine compounds. It is possible to employ a variety of chemical reaction steps so that the sum of them consumes water and heat, produces O2 and H2, and regenerates the chemical reactants within a closed system. The iron-chlorine family of cycles have been considered potentially attractive and investigations are being carried out in Germany, Japan, U.S.A. and Italy. The major attraction of cycles of this family is the fact that the chemicals involved are common and relatively cheap. Our research activities on thermo-chemical cycles are presently focused on the iron/manganese/zinc-chlorine family of cycles. Thermodynamic calculations predict the formation of hematite during hydrolysis of FeCl2 instead of magnetite, and a low production of H2 due to an oxidative atmosphere and a catalytic intervention in the dissociative processes. A feasible way to enhance the H2 production could be by removing the O2 from the reaction site, for example with the presence of an oxygen scavenger. Some works reveal that most support materials exert a catalytic effect on the hydrolysis reaction, resulting in higher degrees of conversion. The main objective of this work has been to analyze the kinetics of thermo-chemical reactions under different physical-chemical parameters, and their influence on the efficiency of H2 conversion. For this purpose, a series of reactions in a new quartz reactor varying the conditions and the presence of different catalysts and oxygen scavengers, were performed and results are presented.