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Conference Article: High temperature heat storage and temperature upgrading by use of CaO/H2O and CaO/CO2 reactions

Ogura, H.; Kanamori, M.; Matsuda, H.; Hasatani, M. (Nagoya Univ., Nagoya (Japan). Dept. of Chemical Engineering)

Abstract

From the view point of utilizing high temperature level heat of nuclear energy, chemical heat pump (CHP) systems are surveyed for high temperature level heat storage and temperature upgrading of the heat. In the present paper, two types of CHP using CaO/H2O/Ca(OH)2 and CaO/CO2/CaCO3 reactions are proposed by considering the reaction temperature level and reaction rates etc. The operating temperature level and heat-releasing/storing rates of a lab-scale heat pump unit using the above mentioned reactions were investigated experimentally and theoretically. It was found that the temperature of the reactant particle bed during the heat-releasing step in the CHP using a CaO/H2O/Ca(OH)2 reaction was rapidly raised up to 870K, when the evaporated H2O vapor pressure was 506 kPa. Regeneration of CaO from Ca(OH)2 during the heat-storing step was well completed at the supplied heat temperature of 773K. It was also recognized that these experimental results were well explained by a derived mathematical model which considers the unsteady state heat conduction accompanied by the exo-/endothermic reaction of the CaO packed bed. For the CHP using CaO/CO2/CaCO3 reaction, the initial temperature of CaO packed bed maintained at 773K was upgraded to 1300K by adjusting the CO2 pressure at 506kPa. Thus, the possibility of CaO/H2O/Ca(OH)2 and CaO/CO2/CaCO3 reactions for high-temperature CHP which will be driven by nuclear thermal energy was shown from a fundamental viewpoint.

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key words: Gas Cooled Reactor, Nuclear Technology
Reference:
Technical committee meeting on high temperature applications of nuclear energy. Oarai (Japan). 19-20 Oct 1992
International Atomic Energy Agency, Vienna (Austria)
IAEA-TECDOC--761, pp:95-102