Nickel-iron modified natural ore oxygen carriers for chemical looping steam methane reforming to produce hydrogen.

Chemical looping steam methane reforming (CL-SMR) is a promising and efficient method to produce hydrogen and syngas. However, oxygen carrier (OC) prepared by synthesis are complex, expensive and poor mechanical performance, while natural ore OCs are low activity and poor selectivity. In order to avoid these problems, Ni/Fe modification of natural ores were proposed to improve the reactivity and stability of OC to CL-SMR. The results indicated that the modified calcite recombined and improved the structural phase during the reaction, enhancing performance and inhibiting agglomeration. Moreover, high ratio of iron to nickel was easy to sinter and decline the OC performance. In addition, with the increase of steam flow, both CH 4 conversion and carbon deposition decreased. Thereinto, the highest H 2 concentration, CH 4 conversion efficiency and H 2 yield were obtained when the ratio of steam to OC was 0.05. Furthermore, CH 4 flow rate had a great impact on CL-SMR performance. When the ratio of CH 4 to OC was 0.04, it achieved the highest CH 4 conversion efficiency of 98.96%, the highest H 2 concentration of 98.83% and the lowest carbon deposition of 3.23%. However, the carbon deposition increased with the increase of CH 4 flow rate. After a long-time chemical looping process, the Ni/Fe modified calcite showed a consistently stable performance with average H 2 concentration of 93.08%, CH 4 conversion efficiency of 88.03%, and carbon deposition of 2.15%. • Natural ores show good performance of oxygen carrier in chemical looping reforming. • High Iron/Nickel is easy to sinter and decline the OC performance. • Steam and CH 4 content have an obvious effect on H 2 production and efficiencies. • Ni/Fe improves the abilities of anti-agglomeration and anti-sintering of calcite. • Ni/Fe modified calcite exhibits an excellent stability performance to produce H 2. [ABSTRACT FROM AUTHOR]