Hydrogen-rich syngas production form biomass char by chemical looping gasification with Fe/Ca-based oxygen carrier

Abstract

Iron based oxygen carrier is attractive for chemical looping gasification due to its abundance, however it suffers low reactivity. Several materials have been utilized in the literatures to solve this issue, of which Ca is promising. In this work, iron has been modified by two Ca ratios to obtain CaFe2O4 and Ca2Fe2O5 oxygen carriers via sol–gel method. Oxygen carriers have compared in hydrogen-rich syngas production form biomass char in a fixed-bed system, and the effect of temperature and cycling ability have also considered. A series of characterizations including X-ray diffraction, scanning electron microscope, H2-temperature-programmed reduction, nitrogen adsorption and desorption and X-ray photoelectron spectroscopy were utilized to investigate the fresh and spent oxygen carriers. The result showed that the CaFe2O4 sample obtained an excellent H2 yield (0.87Nm3/kg) at 750℃ and oxygen carrier: biochar ratio of 1:1. Compared with gas–solid and solid–solid reactions at different temperature, the only CO and CO2 were produced in solid–solid reaction, and the conversion activity of CO into CO2 noticeable increase with raising temperature. On the other hand, the H2 is dominant component on production, and the H2 yield (2.0 Nm3/kg) was a maximum at 850 ℃. In the cycle experiment, the H2 yield was stable through 5th cycles. However, the Si generated by biochar cause the destruction of CaFe2O4, decreasing the CO production and conversion.