Kinetic analysis of a Cu-based oxygen carrier: Relevance of temperature and oxygen partial pressure on reduction and oxidation reactions rates in Chemical Looping with Oxygen Uncoupling (CLOU)

• Kinetic of reduction and oxidation of Cu-based oxygen carrier for CLOU was determined.
• Nucleation and nuclei growth model described solids conversion evolution with time.
• Langmuir–Hishelwood model was able to describe the effect of oxygen concentration.
• Activation energies were 270 and 30 kJ mol−1 for reduction and oxidation respectively.
• A tool for design and optimization of CLOU process was developed using kinetic data.

The kinetic of reduction of CuO to Cu2O with N2 + O2 mixtures and the oxidation of Cu2O to CuO with O2 of a Cu-based oxygen carrier for the CLOU process has been determined in a TGA. For kinetic determination, the O2 concentrations were varied between 0 and 9 vol.% for reduction, and between 21 and 1.5 vol.% for oxidation reactions; temperature was varied between 1148 and 1273 K for the reduction and between 1123 and 1273 K for the oxidation. The oxygen carrier showed high reactivity both in oxidation and reduction reactions. The nucleation and nuclei growth model with chemical reaction control properly described the evolution of solids conversion with time. The Langmuir–Hinshelwood model was able to describe the effect of oxygen concentration on reduction and oxidation rates. The reaction order was 0.5 for reduction and 1.2 for the oxidation. The kinetic constant activation energies were 270 kJ mol−1 for the reduction and 32 kJ mol−1 for the oxidation. The kinetic model was used to calculate the solids inventory needed in the fuel reactor for complete combustion of three different rank coals. It was possible to use a low oxygen carrier inventory in the fuel reactor (160 kg/MWth) to supply the oxygen required to full lignite combustion. However, to reach high CO2 capture efficiencies (⩾95%), oxygen carrier inventories in fuel reactor higher than 600 kg/MWth were needed with the lignite.