Chemical looping combustion (CLC) of two Victorian brown coals – Part 1: Assessment of interaction between CuO and minerals inherent in coals during single cycle experiment

In a series of two papers chemical looping combustion (CLC) of two Victorian brown coals (Loy Yang and Morwell) were investigated using CuO as oxygen carrier. The experiments were conducted using a thermogravimetric analyzer (TGA) under CO2 gasification environment with CuO. This first paper reports the assessment of interaction between CuO and minerals inherent in coals during one reduction and one re-oxidation cycle experiment. The experiments were performed at two different operating temperatures of 800 °C and 950 °C. Also, the time for which the CuO was exposed to experimental environment, was varied. It was observed that at 950 °C CuO could not be re-oxidized to its original state due to sintering that significantly altered the morphology. However, the variation of time did not impact severely on CuO performance in terms of its reactivity and oxygen transport capacity. Gain in weight during the last stage of reduction of CuO with Morwell coal was observed due to strong interaction between minerals in coal and CuO. No such evidence of interaction between Loy Yang coal minerals and CuO was observed. Hence, to further investigate this issue, experiments were undertaken using raw and acid-washed Morwell coals. As expected, no such gain in weight with acid-washed coal was observed as acid washing leached almost all the minerals in coal. The solids resulting from minerals interactions and their morphology were characterized by SEM–EDX. The presence of elements in solid residues, as predicted by thermodynamic simulations under identical experimental conditions, was similar to that observed by EDX. The part 2 of the paper describes the assessment of performance of CuO during multi-cycle experiments.