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Cheap, efficient, and non-toxic energy storage technologies are urgently needed to handle the rapidly increasing penetration of intermittent renewable energies into the grid. This work explores the use of limestone and dolomite for energy storage in concentrated solar power (CSP) plants by means of the calcium looping (CaL) process based on the multicycle carbonation/calcination of CaO. An efficient integration of the CaL process into CSP plants involves high temperature carbonation and calcination at moderate temperatures in a close CO2 cycle for power generation. These conditions differ from those of the CaL process for CO2 capture, which lead to CaO deactivation as extensively reported in recent years. In contrast, we show that limestone- and dolomite-derived CaO give rise to a high residual conversion at CaL-CSP conditions and in short residence times, which would facilitate the development of a competitive and clean CSP technology with permanent energy storage. [ABSTRACT FROM AUTHOR]

Highlights: [•] CaO regenerability is improved by constant rate thermal analysis (CRTA) pretreatment in air/CO2. [•] CRTA pretreatment allows to control mass/heat transfer phenomena. [•] CRTA yields a stable hard skeleton of poorly reactive CaO and a soft skeleton of reactive CaO. [•] Slow activity decay of pretreated CaO is due to sintering in calcination of a renewed soft skeleton. [•] Nanosilica mitigates CaO sintering giving rise to a higher conversion. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Al-based CaO sorbents were prepared by different precursors. • Composites were subjected to calcination/carbonation cycles at realistic CO 2 capture. • SiO 2 and Al 2 O 3 NPs were used to improve the fluidizability of synthesized sorbents. • Dispersion of Ca 9 Al 6 O 18 phase in the sorbent matrix changed the activity of materials. • Adding SiO 2 ≥ 15 wt% and Al 2 O 3 ≥ 10 wt% to the sorbent leaded to uniform APF behavior. Abstract CaO-based materials have been identified as promising sorbents for highly efficient pre-combustion and post-combustion CO 2 capture in fluidized beds operated at high temperatures by means of the Calcium Looping (CaL) process. However, Ca-based sorbents suffer from a decline of the capture capacity over multiple sorption/desorption cycles, mainly due to sintering, and from a markedly heterogeneous fluidization behavior due to the strength of interparticle attractive forces as compared to particle weight. The present study is focused on the development of novel synthetic CaO/Al 2 O 3 sorbents for CO 2 capture with enhanced CaL performance and fluidizability by dry mixing with flow conditioner nanopowders. The influence of initial precursors on the sorbents multicycle activity at realistic CaL conditions has been investigated. The formation of a stable Ca 9 Al 6 O 18 mixed-phase during the preparation of the sorbents promotes the multicycle capture capacity. The type of Ca and Al precursors, either soluble or insoluble, can significantly affect the dispersion of this stabilizer (Ca 9 Al 6 O 18) in the sorbent matrix and, consequently, may affect the carbonation activity of the materials. The sorbent prepared from soluble aluminum nitrate and calcium nitrate precursors by sol-gel method exhibits a very stable multicycle capture capacity with a capture capacity around 0.2 g of CO 2 /g of sorbent after 21 cycles keeping a 72% of its initial capture capacity. The fluidizability of this promising sorbent was also investigated as affected by the addition of three different flow conditioners. Fluidization experiments confirmed the positive effect of using hydrophilic alumina and hydrophobic silica nanoparticles on improving the fluidizability of the synthesized sorbents. [ABSTRACT FROM AUTHOR]