Cu_xMg_1-xFe₂O₄-type spinels as potential oxygen carriers for waste wooden biomass combustion

Waste wood biomass is considered a renewable energy source. Combining biomass combustion with emerging clean combustion technologies such as chemical looping combustion (CLC) can yield effective and affordable carbon capture and, consequently, lead to negative net emissions of greenhouse gases. Oxygen carrier (OC) is a crucial material in CLC technology that must exhibit certain properties, such as high durability, good chemical stability during numerous red-ox cycles and, important for the combustion of solid fuels, the capability of spontaneously releasing oxygen in a process referred to as chemical looping with oxygen uncoupling (CLOU). In this work, a series of nine Cu_xMg_1-xFe₂O₄ spinel-based materials were synthetized and evaluated for the first time as potential OCs for a waste biomass combustion. Their properties, such as oxygen transport capacity and reactivity with biomass (wood chips) as a fuel, were evaluated in a function of temperature (900-1000 °C). Tested oxygen carriers were characterized with an excellent oxygen transport capacity in CLOU process (up to 2.78 wt%) and good reaction rates with the fuel (up to 1.19 wt. %/min), and regeneration rates (up to 3.8 wt. %/min). High conversion of the waste biomass was also achieved (98.9 %). Moreover, new findings revealed a strong positive effect of magnesium addition on mechanical strength (crushing strength > 4 N for samples with Mg content above 0.5).