Fate of trace elements in Oxygen Carrier Aided Combustion (OCAC) of municipal solid waste

•Bottom and fly ashes sampled over a period of 38 days.•Detailed characterization of ilmenite particles using X-ray Photoelectron Spectroscopy.•Effect of bed material, temperature and reduction potential investigated.•Zn is incorporated in the Fe-rich ash layer in ilmenite particles.•Accumulation of Cu observed over time and limited interaction detected with Pb.