Study of selective condensation for woody biomass pyrolysis oil vapours

Abstract

The quality of oil produced from the pyrolysis of biomass is a function of many factors, including the type and extent of the condensing system. In this work, we designed a two-stage fractionation system intermediate/fast pyrolysis in a 2–4 kg/h auger reactor to determine the impact of removal of water and low molecular weight acidic compounds on the quality of the oil and the nature of the fractions recovered. The auger reactor two-stage fractionation system consists of two shell and tube condensers in series with an ESP. The first condenser coolant temperature was varied between 50 and 90 °C, while the second condenser temperate was kept constant at 4 °C. GC-FID analysis show that acetic acid which contributes to bio-oil acidity and other light ends such as methanol, glycolaldehyde, and acetol are entirely removed from the first condenser product at a coolant temperature of 90 °C. The product has a low water content (6 wt%), a low acid content (34 mg KOH/g), and a high heating value (approximately 28 MJ/kg). The two-stage fractional system improves bio-oil fuel quality compared to a bio-oil produced from a traditional condenser system. However, the viscosity of the bio-oil approximately doubled as the first condenser coolant temperature increased from 50 to 70 °C and subsequently limits its applications.