Reactivity study on oxygen carriers for solar-hybrid chemical-looping combustion of di-methyl ether

A power cycle with the solar-hybrid chemical-looping combustion can simultaneously provide a new insight for treating with the problem of large energy penalty for CO2 capture in the energy system and achieve the efficient utilization of the mid-temperature solar thermal energy. Experiments were implemented on a thermo-gravimetrical reactor with di-methyl ether (DME) as fuel to identify suitable looping material for this system. Oxygen carriers, with Fe2O3, NiO, and CoO as solid reactants and Al2O3, MgAl2O4, and YSZ as binders, were prepared by dissolution method. Compared with Fe2O3 and NiO, CoO has higher reactivity in the research temperature range of 673–773 K, and the suitable reduction temperature of CoO with DME is around 723 K. Carbon deposition in the reduction process of DME with CoO/CoAl2O4 can be completely suppressed by adding water vapor to the gaseous reactant, and the optimal range of H2O/DEM is around 1.5–2.0. Scanning electron microscopy was used to characterize the morphological features of the fresh and the cycling used oxygen carriers. For CoO/YSZ, big grains formed after cyclic reactions, but no apparent change was found for CoO/CoAl2O4. The findings of this paper provide a promising looping material candidate for the solar-hybrid chemical-looping combustion.