Chemical Looping Combustion of gaseous and solid fuels with manganese iron mixed oxide as oxygen carrier

Synthetic manganese-iron mixed oxides are considered promising materials to be used as oxygen carriers for Chemical Looping Combustion of coal with carbon dioxide capture at low cost. The aim of this work was to evaluate a manganese-iron mixed oxide material with a manganese to iron molar ratio of 0.77:0.23 as oxygen carrier for coal combustion by means of chemical looping processes, including both ex-situ and in-situ gasification of coal. The preparation method-spray drying followed by calcination was optimized in order to produce particles with high reactivity and mechanical strength. The material was studied in two continuously operated facilities designed to burn either gaseous or solid fuels. While full combustion was achieved burning syngas, showing the feasibility of the use of this material considering the ex-situ gasification process. Coal combustion efficiency by in-situ gasification process was improved in comparison with other previously tested low-cost materials such as ilmenite and iron ore. Moreover, the oxygen carrier particles showed an interesting magnetic behavior that was able to facilitate oxygen carrier recovery from the purge ash stream. In view of these results, the manganese-iron mixed oxide as oxygen carrier is proposed as a promising candidate for use coal combustion by the chemical looping process.