Effect of H2S on Chemical Looping Combustion of Coal-Derived Synthesis Gas over Fe–Mn Oxides Supported on Sepiolite, ZrO2, and Al2O3

The performance of Fe–Mn oxide oxygen carriers supported on sepiolite, ZrO 2, and Al 2 O 3 with simulated synthesis gas/air in a novel combustion technology known as chemical looping combustion (CLC) was evaluated. Thermogravimetric analyses (TGAs) and bench-scale low-pressure (10 psi) flow reactor tests were conducted to evaluate the performance. Multicycle tests were conducted in atmospheric TGA with oxygen carriers using simulated synthesis gas with and without H 2 S. The effect of H 2 S impurities on both stability and oxygen transport capacity was also evaluated. Multicycle CLC tests were conducted in the bench-scale flow reactor at 800 °C with selected samples as well. Chemical-phase composition was investigated by the X-ray diffraction (XRD) technique. Five-cycle TGA tests at 800–900 °C indicated that all oxygen carriers exhibited stable performance. It was interesting to note that there was complete reduction–oxidation of the oxygen carrier during the five-cycle test. Fractional reduction, fractional oxidation, and global reaction rates were calculated from the data. It was found that the support-type had a significant effect on both fractional reduction–oxidation and reaction rate. The oxidation reaction was significantly faster than the reduction reaction for all oxygen carriers. The presence of H 2 S in the synthesis gas resulted in a positive effect on the reaction rate. Bench-scale low-pressure flow reactor data indicate stable reactivity, full consumption of oxygen from the oxygen carrier, and complete combustion of H 2 and CO. XRD data of samples showed stable crystalline phases without the formation of sulfides or sulfites/sulfates and complete regeneration of the oxygen carrier.