Estimation of Enthalpy of Bio-Oil Vapor and Heat Required for Pyrolysis of Biomass

A method is proposed to estimate the enthalpy of bio-oil in the vapor phase, Hbo, as a function of temperature in the range 298.15–1000 K, of which experimental determination has not been done so far. The two equations proposed in this work allow estimation of the standard enthalpy of formation, Hbo,0, and the difference in the enthalpy between 298.15 K and a given temperature, ΔHbo(T), respectively, only based on the overall C, H, and O contents of crude bio-oil of that N and S contents are lower than 0.5 and 0.1 wt %-daf, respectively. These equations were optimized using thermodynamic data of 290 and 141 organic compounds for Hbo,0, and ΔHbo(T), respectively. Given the yields of bio-oil, char, and gas, elemental compositions of the bio-oil and char, and chemical composition of the gas, proposed equations predict the heat required for biomass pyrolysis, Qpy(Tpy), which is defined as the enthalpy difference between the products at the pyrolysis temperature, Tpy, and the biomass at 298.15 K. The predicted Qpy at Tpy = 773–823 K for five different types of dry biomass was in the range of 1.1–1.6 MJ kg–1.