Fast pyrolysis of contaminated sawdust in a circulating fluidised bed reactor

• Contaminated sawdust gave 67 wt% bio-oil yield with 30 MJ/kg LHV.
• Effects of solid and liquid contaminants on pyrolysis products are discussed.
• Mineral oil contaminants led to bio-oil yield increase.
• Bio-oil contained large proportion of hydrocarbons.
• Contaminants increased bio-oil viscosity and LHV and decreased char LHV.

Sawdust contaminated with mineral oils and solids was pyrolysed in a circulating fluidised bed (CFB) reactor. The objectives are to investigate the influences of pyrolysis temperature (400–600 °C) and the contaminants on product yields and properties. The results show that bio-oil reached its maximum yield of 67 wt% at 500 °C and had a lower heating value (LHV) of ∼30 MJ/kg. At this temperature, the char yield of 18 wt% with an LHV of 18 MJ/kg and the gas yield of 15 wt% with an LHV of 28 MJ/Nm3 were obtained. Increasing the temperature tended to reduce the bio-oil water content and stability, while increasing its LHV and viscosity. The presence of mineral oils increased the organic bio-oil yield by suppressing the reaction water and increased the heating value of the non-condensable gas by nearly 3-fold. Both solid and liquid contaminants increased the bio-oil viscosity and LHV and decreased the char LHV. In addition, GC/MS analysis of bio-oils from contaminated sawdust showed the presence of C12-C44 hydrocarbon components.