Effective direct chemical looping coal combustion with bi-metallic Fe-Cu oxygen carriers studied using TG-MS techniques

This paper contains the results of research on a promising combustion technology known as chemical looping combustion (CLC). The noteworthy advantage of CLC is that a concentrated CO2 stream can be obtained after water condensation without any energy penalty for CO2 separation. The objective of this work was to prepare novel bi-metallic Fe-Cu oxygen carriers and to evaluate the performance of these carriers for the CLC process with hard coal/air. One-cycle CLC tests were conducted with supported Fe-Cu oxygen carriers in thermogravimetric analyzer (TG) utilizing hard coal as a fuel. The effects of the oxygen carrier chemical composition, particle size, and steam addition on the reaction rates were determined. The fractional reduction, fractional oxidation, and the reaction rates were calculated from the TG data. Notably, the support had a considerable effect on the reaction performance. Moreover, bi-metallic Fe-Cu oxygen carriers exhibited significantly improved reactivity compared with monometallic Fe oxygen carriers. Furthermore, the addition of a second reactive metal oxide stabilized the oxygen carrier structure. The oxidation reaction was significantly faster than the reduction reaction for all supported Fe-Cu oxygen carriers. The TG data indicated that these oxygen carriers had stable performances up to 900 A degrees C and may be effectively used for direct coal CLC reactions.