Thermodynamic modeling of the condensable fraction of a gaseous effluent from lignocellulosic biomass torrefaction

The condensable fraction of the gaseous effluent from the torrefaction process of wood is a complex mixture of more than one hundred oxygenated species (alcohols, acids, aldehydes, ketones, furans, phenolic, gaïacols and sugars) diluted in water where some of them are likely to react. This effluent is currently burnt to provide energy but it could be valorized as bio-sourced chemicals. To recover target products like acetic acid, glycolaldehyde, furfural and eugenol a first step of thermodynamic modeling of this complex mixture is required to be able to propose different strategies of separation-purification. This was done here by coupling the UNIQUAC model with chemical equilibria involved in the reactive mixture. Binary interaction parameters were identified using vapor–liquid equilibria data from the literature. The predicted results are in good agreement with the experimental data of systems containing water, methanol, formaldehyde, acetic acid, formic acid, propionic acid, furfural and furfuryl alcohol, main components of the considered mixture and their associated reaction products.