Enhanced performance of manganese ore as oxygen carrier for chemical-looping with oxygen uncoupling (CLOU) by combination with Ca(OH)2 through spray-drying

The two combined materials behaved differently from their natural counterparts. The Brazilian ore + Ca(OH)2 showed a decrease in reactivity towards methane, but higher reactivity towards syngas in comparison to the pure ore. The South African ore + Ca(OH)2 showed a major improvement in reactivity towards both syngas and methane, which could be attributed to formation of a perovskite-structure material with significant CLOU properties. A comparison between the pure ores and the combined materials show that the addition of Ca(OH)2 had generally a beneficial impact on the mechanical stability of the oxygen carriers. As a significant change in the particle size distribution was seen for all oxygen carrier materials after repeated redox cycles with long reduction periods, the particle disintegration was likely caused by the chemical phase transformations occurring inside the particles, rather than by mechanical forces.