Effect of in-situ addition of alcohol on yields and properties of bio-oil derived from fast pyrolysis of eucalyptus bark

•Without alcohol addition, eucalyptus bark gave 60 wt% bio-oil yield.•Effects of alcohol feeding positions, types and content are discussed.•In-situ addition of alcohol was more effective than external mixing.•Bio-oil properties were improved with the in-situ alcohol feeding.•5 wt% in-situ addition was better than external blending at 30 wt%.

Fast pyrolysis of eucalyptus bark using a free-fall reactor integrated with an in-situ alcohol feeding unit was studied to investigate the effects of feeding positions (in-situ and external), alcohol types (ethanol and methanol) and alcohol content (5–30 wt%) on bio-oil yield and properties. The results show that the bio-oil yield decreased with alcohol content from 60 wt% (without alcohol) to 40 wt% with 30 wt% alcohol, whereas the gas yield increased and the char yield remained constant. In-situ addition of alcohol was more effective than external mixing in terms of bio-oil viscosity, stability, water content and pH. Feeding 5 wt% alcohol into the process gave similar or better results than external mixing with 30 wt% alcohol. Nearly 70% of the viscosity and 30% of the water content were reduced with 5 wt% methanol added into the process. The heating value, specific gravity, ash and solids contents were similarly improved by the in-situ and external addition.

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