Vapor-Liquid Phase Equilibrium of Fast Pyrolysis BioOils ? Experiment and Modelling

ILLE, YANNIK; SÁNCHEZ, FRANCISCO; VELEZ, ALEXIS; PEREDA, SELVA; DAHMEN, NICOLAUS; SCHABER, KARLHEINZ

Radisson Blu Aqua, Chicago, Illinois

Conferencia; The International Conference on Thermochemical Conversion Science, tcbiomass 2017; 2017

Fast pyrolysis is an option to convert lignocellulosic biomass into a large fraction of liquid bio-oil besides some char/ash and non-condensable gas. When ash-rich material is used, this usually results in a higher water content of the pyrolysis oil and a possible phase separation. To avoid phase separation, fractional condensation systems have been developed. Choosing appropriate condensation temperatures is essential to reach the desired water content and bio-oil composition. For the modelling of such systems, detailed knowledge about the phase equilibrium of pyrolysis vapors and oils is necessary. Due to the complexity and highly non-ideal behavior of biomass derived mixtures, this is a challenging task. Additional the specification of a suitable model mixture is required.In this work straw based bio-oils from the bioliq fast pyrolysis process are investigated in a phase equilibrium cell. The results are used for the evaluation of suitable model mixtures and thermodynamic models. Particularly, model molecules for the pyrolytic lignin are of interest, as this fraction is not yet completely analyzed but is expected to have a big influence on the activity of the more volatile components. 195 model molecules for the pyrolytic lignin and two group contribution based thermodynamic models, Modified UNIFAC and GCA-EoS, are compared. While Modified UNIFAC is a GE-model, GCA-EoS is an equation of state, which specifically describes association effects. As a result, experimental and calculated data is presented and compared, with the focus on the activity of water as a key property for the thermodynamic behavior. For the bio-oil investigated in this work 4,4?-Biphenol is found to be best suited as a model molecule representing the pyrolytic lignin. Depending on the model molecule, the results can differ more than 100%. This demonstrates the importance of a carefully chosen model mixture as an indispensable fundament for any simulation dealing with fractional condensation systems.