Effect of iron on Shengli brown coal char structure and its influence on gasification reactivity

Acid-washing brown coal samples loaded with different content of iron catalyst were pyrolyzed in a fixed bed reactor. The effect of iron on coal char functional group, carbon crystallite structure, surface active site and gasification reactivity were investigated by FT-IR, Raman spectra,TPD and TG. FT-IR results reveal that the numbers of -OH、-CH₃、-CH₂ active functional groups increase significantly during catalytic pyrolysis. Raman spectra results show that I_G/I_all reduces from 0.095 to 0.087 and I_D3/I_all increases from 0.090 to 0.097 with the increase of iron loading, respectively. It means that partial large polyaromatic ring structures transform into small polyaromatic ring structures under the catalytic action of iron. TPD experimental results indicate that the numbers of active sites increase with the increase of iron loading. With 3% Fe loading, the numbers of active sites rise with the increase of adsorption temperature until 800 ℃, and then start to decrease. The adsorption quantity of CO₂ increases with time at 750 ℃, and reaches saturated adsorption state after 45 min. Coal char-steam isothermal gasification experiment result suggests that the gasification reactivity of coal char has a close relationship with the number of active sites, and the iron catalyst can enhance the char gasification reactivity by increase the number of surface active sites.