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CPOTE2020 logo
6th International Conference on
Contemporary Problems of Thermal Engineering
Online | 21-24 September 2020

Abstract CPOTE2020-1053-A

Book of abstracts draft
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SrO-Al2O3 composites for thermochemical energy storage: carbonation kinetics

Federica RAGANATI, Consiglio Nazionale delle Ricerche (CNR), Italy
Paola AMMENDOLA, Consiglio Nazionale delle Ricerche (CNR), Italy
Francesco MICCIO, Consiglio Nazionale delle Ricerche (CNR), Italy
Annalisa NATALI MURRI, Consiglio Nazionale delle Ricerche (CNR), Italy
Elena LANDI, Consiglio Nazionale delle Ricerche (CNR), Italy

The main challenge for a short-term deeper penetration of renewable energy sources, such as solar energy, typically characterized by the intermittency of power production, is represented by energy storage. In this framework, thermochemical energy storage (TCES) is considered as a promising technology to accomplish high-energy storage efficiency in concentrating solar power (CSP) plants. It consists of using the high temperatures achievable by CSP to drive an endothermic chemical reaction. The reaction products are stored separately to be employed when needed for carrying out the exothermic reverse reaction, which releases the heat previously accumulated. Among all the possible alternatives, the reversible dissociation/carbonation of metal carbonates, carried out in fluidized bed reactors, is of paramount relevance for thermochemical energy storage in concentrating solar power plants. In this framework the SrCO3/SrO system is receiving great research interest due to its high energy density (4 GJ m-3) and working temperatures (up to 1200 °C). In analogy to the more investigated CaCO3/CaO couple, one of the main problem of SrO is that particle sintering causes a dramatic drop of its reactivity over multiple carbonation/calcination cycles. In this context, much effort has already been devoted to the material characterization and improvement of its multicycle conversion and stability, such as the incorporation of refractory inert materials serving as sintering inhibitors. In particular, it was shown that Al2O3 can be successfully used as sintering and agglomeration inhibitor to improve the performances of the system SrO/SrCO3. In this work, the gas-solid kinetics of SrO carbonation, the slowest and bottle-neck step in the cycle, has been investigated in thermogravimetric and lab-scale fluidized bed equipment. In particular, experimental tests have been performed using a SrO-Al2O3 composite containing 34%wt of Al2O3, which has been previously proved to be stable over repeated carbonation/calcination cycles. Moreover, it has shown a good stability also from the mechanical point of view, thus being able to withstand fluidized bed operation without raising noteworthy attrition and/or elutriation issues. Then, a simple apparent kinetic model approach has been applied to fit the experimental conversion data, thus obtaining useful information for design and optimization of the SrO carbonation reactor.

Keywords: Thermochemical energy storage (TCES), Carbonation kinetics, Strontium oxide, Fluidized bed, Sintering