Biogas combustion in a chemical looping fluidized bed reactor

Chemical looping combustion (CLC) is a process in which oxygen required for combustion of a fuel is supplied by the metal oxide. Metal oxide plays the role of an oxygen carrier by providing oxygen for combustion when being reduced and is then re-oxidized by air in a separate reactor. Combustion is thus without any direct contact between air and fuel: as a consequence flue gas does not contain nitrogen of air which simplifies flue gas treatment prior to sequestration. In the present study, biogas combustion was analyzed in a chemical looping combustion fluidized bed reactor. NiAl0.44O1.67 and Cu0.95Fe1.05AlO4 metal oxide particles were used as oxygen carriers. The experiments have shown the feasibility of biogas combustion in chemical looping combustion: CH4 of the biogas was completely converted to CO2 and H2O with a small fraction of CO and H2. The outlet flue gas distribution profile was not affected by ageing during the cycles of reduction and oxidation, indicating the chemical stability of the oxygen carriers. There was limited formation of carbon on the oxygen carriers during reduction.