Redox performance of Na-modified Fe2O3/Al2O3 with syngas as reducing agent in chemical looping combustion process

Abstract

The redox performances of 1–10 wt% Na-modified Fe2O3/Al2O3 oxygen carrier from seawater were investigated using syngas/air as reactive gases in the thermogravimetric analyzer (TGA) and lab-scaled semi-fluidized bed reactor (semi-FzBR). NaNO3(aq) as the source of sodium dopants to prepare Na-contained solution was implemented by an air atmospheric pressure plasma jet (Air-APPJ) process, which can increase the feasibility of seawater. For the prepared samples, the materials properties, including crystalline phases, surface morphologies, surface areas, and attrition loss performances were well correlated with the Na contents. The results indicated that the poor reduction kinetics and attrition resistance were obtained with the Na adjunction over 5 wt%, attributing to the sintering issue on excessive phases of Na2(Al, Fe)12O19 and Na(Al, Fe)O2 solid solution in the samples. Therefore, the slight incorporation of Na content in the Fe2O3/Al2O3 samples which improved the reduction rate was proved as the candidate oxygen carriers. Particularly, the Na content with 1 wt% in Fe2O3/Al2O3 sample (Na1FA32) can significantly promote the reduction behavior, thermal stability, and attrition resistance as compared to the raw Fe2O3/Al2O3 oxygen carrier. It is environmentally beneficial to use the Na1FA32 as oxygen carrier in a practical chemical looping combustion process.