Iron-rich copper ore as a promising oxygen carrier for chemical looping combustion of methane

Chemical looping combustion (CLC) has been considered as a revolutionary combustion technology for low-energy capture of CO2. In this paper, an iron-rich copper ore, mainly containing CuO, CuFe2O4, SiO2 and Al2O3, was used as an inexpensive oxygen carrier (OC) for chemical looping combustion of methane. The activity for methane oxidation, the stability during long-term CLC testing and the structural evolution after redox cycling were systematically investigated. In addition, kinetic study via a thermogravimetric analyzer (TGA) method was also performed on the recycled oxygen carrier to understand the reduction mechanism. The results show that the iron-rich copper ore OC can oxidize methane with very high selectivity (CO2 selectivity > 95%), conversion (CH4 conversion = 80%) and stability in the successive CLC process. No obvious sintering is observed after 30 redox cycling. This can be attributed to the enhanced diffusion of different components (Cu, Fe, Si and Al) in the redox process, which could improve the interaction between the active components (CuFe2O4 and CuO) and the support components (SiO2 and Al2O3). The kinetic study shows that a nucleation-growth model and a diffusion-controlled model can be successfully adapted to depict the reduction of CuO and Fe2O3 in the copper ore OC, respectively. The activation energies for CuO and Fe2O3 reductions are 56.49 and 109.56 kJ/mol, respectively, which are similar with that for the synthetic CuO-based or CuFe2O4-based OCs. This work fully demonstrates the feasibility of using iron-rich copper concentrate as a lower cost OC for the CLC system. (C) 2019 Taiwan Institute of Chemical Engineers. Published by Elsevier B.V. All rights reserved.