Evaporation of biomass fast pyrolysis oil: evaluation of char formation

Evaporation experiments of biomass fast pyrolysis oil and its aqueous fractions at low (TGA-10°C/min, Glass tube-100°C/min) and high (atomization ~10 6°C/min) heating rates are performed. Slow heating of pyrolysis oil produced ~28% char (on carbon basis), whereas atomization of oil droplets (~117µm) produced ~9% char in the temperature range of 500-850°C. Aqueous fractions and glucose solutions also produced less amount of char by evaporating at higher heating rates (~3% char) when compared with slower heating (~24% char). The results obtained show that not a single lumped components class in pyrolysis oil can be identified that is primarily responsible for the char formation. At low heating rate, higher concentrations of organics in the bioliquids result in higher char yields, which reveals that a certain fraction in the oil produce char with a reaction order higher than one (polymerization reactions). The measured trends in char yield can be described by a model in which certain fraction of oil is converted by two parallel reactions to char and gas/vapor.