Effect of preparation of iron-based oxygen carriers on its agglomeration behavior with application to biomass chemical looping gasification

Abstract

Iron-based oxygen carrier (OC) plays a crucial role in biomass chemical looping gasification (BCLG) to produce high quality syngas. However, a significant challenge during BCLG is the OC deactivation due to agglomeration, which is an urgent problem to be solved. In this study, the agglomeration behavior of iron-based OC preparation during the application for BCLG was obtained under the investigation of different preparation methods, carriers and ratios of active metal to carrier. The results revealed that preparation method affected the dispersion, crystal structure and stability of OC, thereby affecting the agglomeration. Among four preparation methods, the OC prepared by co-precipitation method achieved a 58.57 % lower agglomeration degree and 38.38 % smaller particle size than that of mechanical mixing method. Moreover, the carrier played a role in structural support and lattice oxygen transport, affecting crystalline structure and the agglomeration. Among four carriers, the OC prepared with Al2O3 carrier exhibited 36.18 % lower agglomeration degree and 25.15 % smaller particle size than that of CeO2 carrier. In addition, higher Fe content would weaken the metal-carrier interaction and reduce the structural stability of OC, causing serious agglomeration. With the decrease of Al:Fe molar ratio, the average particle size and agglomeration degree of spent OC increased by 43.56 % and 78.26 %, respectively. With the increase of cycles, the average particle size and agglomeration degree of spent OC increased gradually, while the reaction performance decreased obviously.