Solid Phase Heat Recovery and Multi Chamber Reduction for Redox Cycles

Abstract

A system approach was used for the development of a new process concept for solar driven thermochemical redox cycles. Two aspects of this concept will be presented here. Since a high heat recovery rate for cycles using non-stoichiometric reduction has been identified as elementary in order to reach meaningful overall process efficiencies, a special focus was directed on this aspect. A quasi-countercurrent heat recovery system, which makes use of a particulate heat transfer medium, was outlined and numerically analyzed. The analysis shows that recovery rates of more than 70% seem realistic. Even though the heat recovery system is based on an arrangement of stages including relative complex flow pattern the basic principle seems promising and opens up new pathways for system design and optimization. The second aspect highlighted of the developed process concept is the use of a multi chamber system with optimized reaction conditions for the reduction of the redox material. By optimizing the pressure in a multi chamber system energy savings related to the pumping work of more than 20% are predicted. Also the execution of pre-reduction in the heat recovery system is discussed.