Bio-oil yield and quality enhancement through fast pyrolysis and fractional condensation concepts

The influence of operating conditions on the yield and quality of bio-oil obtained from black spruce wood mixture was studied using an auger reactor. Fast pyrolysis optimization through response surface analysis was carried out with four variables: pyrolysis temperature, solids residence time, nitrogen flow, and temperature of first stage of condensation. The optimal conditions obtained for bio-oil production were 555°C, 129 s, 6.9 L/min, and 120°C, respectively. The product yields were 38.61 wt.% of biochar, 25.39 wt.% of liquid, and 36.52 wt.% of non-condensable gases. Two liquid products were produced at the exit of the two condensers, following the concept of fractional condensation. The oily phase yield recovered in the first condenser was 10.59 wt.%, with a 16.86 wt.% of moisture content. Physical properties of the oily phase were analyzed and compared with the ASTM standard D7544-12. Qualitative identification of chemical compounds was carried out for the oily phase which helped in pyrolysis optimization for the bio-oil production targeted towards its use as fuel in commercial burners. In addition, the oil produced here is one of the lowest in water and solids content, attributable to the unique feature of auger reactors without the need for additional treatments.