Chemical looping gasification of biomass char for hydrogen-rich syngas production via Mn-doped Fe2O3 oxygen carrier

Because of its low cost, an iron-based oxygen carrier is a promising candidate for hydrogen-rich syngas production from the chemical looping gasification of biomass. However, it needs modification from a reactivity point of view. In this study effect of Mn doping on Fe2O3 has been investigated for hydrogen-rich syngas production from biomass char at different temperatures (700–900 °C) and steam flow rates (60–100 μL/min). Several techniques (XRD, XPS, BET, and TPR-H2) have been utilized to characterize fresh and spent oxygen carriers. The result demonstrated Mn-doing boosted the redox activity and the amount of oxygen vacancies, which increased hydrogen gas generation. Hydrogen production displayed different behavior across temperatures due to detecting Fe2O3 and MnFeO3 phases for spent oxygen carriers. For the Fe2O3 oxygen carrier hydrogen gas yield is 1.67 Nm3/kg which is due to reduction of Fe2O3 phase to Fe3O4. However, the MnFe2O4 spinel phase detected in the spent MnFeO3 oxygen carrier is a reason for improving hydrogen gas yield to 1.84 Nm3/kg. Change reaction temperature from 900 °C to 850 °C reduced hydrogen gas yield from 1.84 Nm3/kg to 1.83 Nm3/kg for with MnFeO3 oxygen carrier. Regarding different steam flows, the proper flow rates that can maintain the formed phases and obtained best hydrogen gas yield are 80 and 90 μL/min, respectively. Meanwhile, the best hydrogen gas yield (2.21Nm3/kg) are obtained with MnFeO3 oxygen carrier at optimum conditions (850 °C and 90 μL/min).