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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]

Biochar chemical looping gasification (CLG) is a novel technology to obtain hydrogen-rich syngas, high gasification efficiency and low carbon deposition. This study investigates the effect of preparation methods, Fe loadings, active components, Ca loadings and steam/biochar (S/C) to achieve the optimal oxygen carrier. The results show that coprecipitation is the best preparation method to gain highest efficiency, redox activity and dispersion. H 2 production increases visibly with the increase of Fe loading, while efficiencies increase firstly and then decrease. There is an evident effect of active component on CLG. Oxygen carrier based on Fe/Ca performs a lower carbon deposition, higher H 2 production and efficiency. With the increase of Ca loading, H 2 production and efficiencies increase firstly and then decrease. S/C has an obvious effect on CLG performance. 1.5 is the optimal S/C to achieve high H 2 concentration of 67.35%, the highest gas production of 1.34 Nm3/kg and gasification efficiency of 96.93%. Image 1 • Fe/Ca-based oxygen carrier performs synergistic catalysis in biochar CLG process. • Coprecipitation method is conducive to dispersion, redox reaction and efficiency. • The optimal Fe loading is 1.5 with the highest efficiency and interaction of carrier. • 1.0 is the best Ca loading to gain highest efficiencies and lowest carbon deposition. • Steam/biochar has an obvious effect on H 2 production and efficiencies. [ABSTRACT FROM AUTHOR]

• HY zeolite is the best carrier to convert wood vinegar into H 2 -rich syngas by CLR. • Ni/HY has excellent redox performance and gasification efficiency during CLR. • The optimal Ni loading is 20% with the highest H 2 yield and gasification efficiency. • +15% is the best water volume for CLR on crude wood vinegar. • Carbon deposition of Ni/HY at 900 °C for long-time reaction is the lowest. The crude wood vinegar contained a large amount of water and a small amount of complex organic compounds, which was difficult to industrialize practically. An efficient oxygen carrier was prepared by Ni-modified HY zeolite (Ni/HY) to produce hydrogen-rich syngas by chemical looping reforming (CLR) on crude wood vinegar. The yield of gas, conversion efficiency, H 2 /CO, oxygen carrier structure and carbon deposition were investigated to obtain the optimal preparation of oxygen carrier and the optimal CLR performance. The results showed that HY zeolite was the most suitable carrier for CLR among five different molecular sieves. Compared with HY zeolites modified by different metallic oxides, Ni/HY had the highest H 2 yield of 64.68%, gasification efficiency of 85.29% and structural characteristics. Further, water volume had a great impact on the CLR performance. The optimal water volume was + 15% with H 2 yield of 68.4%, carbon conversion efficiency of 37.58% and gasification efficiency of 92.38%. Furthermore, the particle size of oxygen carrier increased with the increase of Ni loading. The best performance with gasification efficiency of 96.17% and carbon conversion efficiency of 39.41% could be obtained when the Ni loading was 20%. Moreover, the CO yield, gasification efficiency and carbon conversion efficiency gradually increased with temperature increasing. After CLR for the long-term reaction time, 900 °C was the best reaction temperature to achieve gasification efficiency of 107.29% and the lowest carbon deposition of 3.71%. [ABSTRACT FROM AUTHOR]

The chemical looping gasification (CLG) of rice husk was conducted in a small fixed-bed reactor to investigate the effects of oxygen carrier preparation methods, active components, Fe loadings, water inflow and successive redox cycles. The gas content, the relative gas concentration, lower heating value of syngas (LHV), carbon conversion efficiency, gasification efficiency, H 2 -TPR, XRD, BET and SEM were analyzed to obtain CLG reaction characterization and comprehensive performance of oxygen carrier. The results showed that compared with several methods and active components, the coprecipitation method with a Fe:Al ratio of 2 was the best preparation method for oxygen carrier. Furthermore, the H 2 concentration was 57.29%, while the gasification efficiency and carbon conversion efficiency were 95.79% and 51.56%. Meanwhile, the oxygen carrier prepared by coprecipitation had a greater performance of oxygen release and reduction. There was an optimal water inflow to obtain the highest gas content, carbon conversion efficiency and gasification efficiency. Thereinto, the H 2 concentration was stable at 54.07–57.65%. And the highest gas content of 78.33% and carbon conversion efficiency of 54.42% were obtained at a water inflow of 14.0 mL/h, while the highest gasification efficiency of 95.79% was obtained at 16.8 mL/h. In addition, after ten successive redox cycles, the gasification performance, crystal size, specific surface area and pore structure were relatively stable. Moreover, the material composition remained basically unchanged. • Coprecipitation is the best preparation method to gain the highest H 2 concentration. • Fe is the optimal active component to gain a highest H 2 concentration and efficiency. • Al:Fe of 2:1 is the best Fe loading in oxygen carrier for a great performance. • Water inflow is beneficial to increase the H 2 concentration. • Reaction performance and structure are stable after ten successive redox cycles. [ABSTRACT FROM AUTHOR]