Hydrogen-rich gas production by steam gasification of char derived from cyanobacterial blooms (CDCB) in a fixed-bed reactor: Influence of particle size and residence time on gas yield and syngas composition

Char derived from cyanobacterial blooms (CDCB), by-product of fast pyrolysis of cyanobacterial blooms from Dianchi Lake (Yunnan Province, China) at a final pyrolysis temperature of 500 °C were used as feedstock material in this study. Steam gasification characteristics of CDCB were investigated in a fixed-bed reactor to evaluate the effect of particle size (below 0.15 mm, 0.15–0.3 mm, 0.3–0.45 mm, 0.45–0.9 mm, 0.9–3 mm) and solid residence time (3, 6, 9, 12, 15 min) on gas yield and composition, and experiments were carried out at bed temperature range of 600–850 °C, steam flow rate of 0.178 g/min. The results showed that solid residence time played an important role on steam gasification process, while particle size presented less effect on gasification process; proper particle size and longer residence time were favorable for dry gas yield and carbon conversion efficiency (CCE). At the same time, higher reaction temperature reduced influence of particle size on gasification process, and smaller particle size required less residence time for reaction completed. Maximum dry gas yield and CCE reached 1.84 Nm³ kg⁻¹ and 98.82%, respectively, achieved at a temperature of 850 °C, flow rate of 0.178 g/min, solid residence time of 15 min and particle size range of 0.45–0.9 mm.