TGA AND KINETIC MODELLING OF CO, MN AND CU OXIDES FOR CHEMICAL LOOPING GASIFICATION (CLG)

Oxygen carriers for biomass gasification are capable of absorbing oxygen from air and desorbing it in the gasifier. Based on thermodynamic equilibrium, copper, manganese, and cobalt oxides have the highest oxygen release capacities among the different oxygen carriers. These oxygen carriers were deposited on alumina via incipient wetness impregnation. The weight loss of the CuO-Cu2O carrier, as measured in a thermo-gravimetric analyzer, was 10% while it was 7% for the Co3O4-CoO couple and only 3% for the Mn2O3-Mn3O4 couple. The optimum operating temperature for the CuO oxygen carrier was 100 degrees C higher compared to the other two at 950 degrees C. A modified nuclei growth model (MNG) characterizes the weight loss/gain during the reduction-oxidation cycles. The reduction rate is 3 times higher at 875 degrees C compared to 825 degrees C while the oxidation rate decreases more than 10 times. The CuO carrier surface area decreased by 70%, while it was 30% and 60% in the Co3O4 and Mn2O3 carriers, respectively. Cobalt has a lower tendency to sinter at high temperature compared to either copper or manganese and has a higher oxygen transport capacity and oxidation-reduction rates. Therefore, despite its higher cost and toxicity, it might be considered as a potential oxygen carrier especially for solid fuel gasification.