Effect of equivalence ratio on the CO selectivity of Fe/Ca-based oxygen carriers in biomass char chemical looping gasification. (15th September 2019)

• Record Type: Journal Article
• Authors: Xue, Nan; Wang, Zhiqi; Wu, Jingli; He, Tao; Zhang, Jinzhi; Li, Jianqing; Wu, Jinhu
• Is Part Of: Fuel. Volume 252(2019)
• Page Start: 220
• Page End: 227
• Publication Date: 2019-09-15
• Subjects: Chemical looping gasification -- Fe/Ca-based oxygen carriers -- Equivalence ratio -- CO selectivity -- Thermodynamic analysis; Fuel -- Periodicals; Coal -- Periodicals; Coal; Fuel; Periodicals; 662.6
• DOI: 10.1016/j.fuel.2019.04.103
• Languages: English
• ISSNs: 0016-2361

Abstract

Highlights: Three Fe/Ca based oxygen carriers were used for biomass char CLG. Effect of ER on the evolved gas composition of three oxygen carriers was studied. Different oxygen carriers exhibit different performances with different ER. The CO selectivity of CaFe2 O4 had little changes with a wide range of ER. The CO selectivity of Fe2 O3 decreased markedly with increasing ER. Abstract: Equivalence ratio is one of the important operating parameters for biomass gasification. The oxygen carrier possesses high producer gas production in a wide range of equivalence ratio (oxygen carrier/biomass ratio), which is exceedingly desirable for biomass chemical looping gasification (CLG). In this study, the effect of different equivalence ratios on the CO selectivity (the evolved gas composition) of Fe2 O3, Fe2 O3 /CaO and CaFe2 O4 oxygen carriers in biomass char CLG was investigated in a fixed bed reactor. The results showed that the CO selectivity of CaFe2 O4 had little changes and decreased from 70.39% to 59.79% and 73.40% to 63.98% with increasing equivalence ratio from 0.5 to 3.0 at 900 °C and 1000 °C, respectively. In sharp contrast, the CO selectivity of Fe2 O3 changed markedly, which declined respectively from 65.86% to 31.13% (900 °C) and 69.68% to 47.27% (1000 °C). Fe2 O3 /CaO illustrated the similar tendency as Fe2 O3 at 900 °C but as CaFe2 O4 at 1000 ℃. The three oxygen carries exhibited a high CO production at lower equivalence ratio, and CaFe2 O4 displayed the best performance of CO selectivity in the given equivalence ratio range. X-ray diffraction (XRD) spectrums showed that the oxygen carriers were transformed to different iron phases with difference equivalent ratios. The Fe (III) in the three oxygen carries was reduced completely to Fe (0) at the equivalence ratios of 0.5 and 1.0, while FeO and Ca2 Fe2 O5 were the dominant species in the spent oxygen carriers as equivalence ratio was further increased. The trends of CO selectivity obtained by thermodynamic analysis for three oxygen carries were consistent with the experimental results.