Effects of hot filtration on yield and quality of bio-oil from fast pyrolysis of chinese fir in fluidized bed reactor

A hot filter was added to a 1 kg/h bench-scale continuous bubbling fluidized bed system for the fast pyrolysis of Chinese fir to get bio-oils. The effects of hot filter on the yield and stability of bio-oils were studied. The results indicated that both the yields of pyrolysis oil (without hot filtration) and filtered oil (after hot filtration) increased with the increase of pyrolysis temperature, and decreased after 475, at which the maximum yields were 58.1% and 50.7%, respectively. The addition of hot filter resulted in lower oil yield (approximate 5%-10% decrease), which became worse when pyrolysis temperature increased. Compared to the pyrolysis-oil I, the water content of filtered-oil I increased from 13.77% to 15.83%, pH value increased from 2.18 to 2.23, and high-heating value decreased from 20.47 MJ/kg to 19.53 MJ/kg. However, it also showed significant reduction in solids contents, alkali and alkaline earth metals, and the overall decline was about 75%, which suppressed the happening of self-polymerization in bio-oils. During the aging tests, water content and kinematic viscosity of filtered-oil I increased by 10.2% and 57.6%, but the fluctuation was less than that of pyrolysis-oil I. GC/MS analysis of the bio-oils showed that less fluctuation in composition was observed in the filtered-oil I. This indicated a positive impact of the hot filter on the quality of bio-oil. ©, 2015, Editorial Board of Chemistry and Industry of Forest Products. All right reserved.