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International audience; A new torrefaction model was proposed for predicting solid mass loss in torrefaction as a function of biomass main macromolecular composition and type, as well as on the operating conditions. To do this, solid degradation kinetics were modelled following a 2-successive reaction scheme for each macro-compound and the additive modelling approach through biomass macromolecular component behavior in torrefaction proposed by Nocquet et al. (2014). The use of extracted fractions from different woody and agricultural biomass species (ash-wood, beech, miscanthus, pine and wheat straw) instead of commercial compounds increased the accuracy of the prediction of solid kinetics in biomass torrefaction. The validation of the proposed model with 9 raw biomasses in torrefaction showed an accurate prediction for woods, while the prediction for agricultural biomasses was acceptable.

L'invention concerne un procédé de production d'eugénol comportant les étapes suivantes: a/ séchage d'une biomasse humide; b/ torréfaction de la biomasse séchée selon l'étape a/; c/ condensation étagée, des vapeurs issues de la torréfaction selon l'étape b/, la condensation étant réalisée dans au moins deux étages en série à des températures comprises entre 170 et 230 ° C dans le premier étage et entre 110 et 130° C dans le deuxième étage, en aval du premier étage, la récupération des sucres liquides étant réalisée en sortie du premier étage, tandis que la récupération du mélange liquide constitué de l'eugénol et des autres condensats étant réalisée en sortie du deuxième; d/ purification du mélange récupéré selon l'étape cl, afin de récupérer l'eugénol. L'invention concerne également une installation de mise en oeuvre du procédé.

In the context of modelling biomass conversion processes, the accurate representation of biomass, which is a complex and highly variable material, is of crucial importance. This study provides a rather simple and flexible way to represent biomass, especially suited in the context of thermochemical conversion processes. The procedure to represent the enthalpy of formation, the Gibbs free energy and the exergy of biomass in terms of its elemental composition (C, H, O, N, S) and moisture content is outlined. The correlations relating the heating value to the elemental composition of biomass are evaluated through a database of over one hundred raw and pretreated biomass samples. Results show that such correlations can predict the higher heating value (HHV) within an accuracy of 1.93% and 2.38%. One of the correlations is then applied to represent the enthalpy of formation of biomass as a linear function of the elemental composition. The procedure is extended to estimate the Gibbs free energy of formation and subsequently the exergy of biomass, which are expressed as linear functions of the elemental composition. The method proposed for the estimate of exergy allows taking directly into account the composition of the reference environment. Results show that the method proposed in this study agrees within 1% accuracy with the widely used correlation proposed by Szargut et al. (1988). The values obtained for Exergy, over the range of compositions of the samples considered, vary in general between 105% and 115% of the lower heating value (LHV) and 103% and 107% of the higher heating value obtained using the literature correlation by Boie (1953). On the basis of these correlations, this study provides the thermodynamic properties of C, H, O, N, S and bound water ‘pseudo-compounds’ that can be used in the thermodynamic properties evaluation packages used in flowsheeting software and in numerical simulations for a coherent description of biomass as a function of its composition.

Renewable diesel productions through HTL (hydrothermal liquefaction) and pyrolysis of Chlamydomonas reinhardtii were compared based on energetic and economic evaluation. The whole biofuel production pathway was simulated, from the microalgae cultivation step to the upgrading of the bio-oil. Alternative dewatering technologies were evaluated to decrease the energy consumption and the bio-diesel cost. Thermochemical models were developed for both HTL and pyrolysis of C. reinhardtii based on experimental results. The pathways using heat exchangers between the inlet and outlet of the HTL reactor were the only scenarios to be net energy producers. The other pathways consumed more energy than they produced. The costs of production of renewable diesel from HTL or pyrolysis were significantly higher than petroleum diesel (average of 70.4 €/GJ). The most expensive step was the microalgae cultivation (nutrients cost and raceway capital cost).

This study presents a methodology relying on thermodynamic analysis to carry out a preliminary screening of biomass conversion pathways, that is, before the detailed design of the process itself. The approach allows to sensibly set process integration targets by evaluating thermodynamic limits. Several case studies are presented for the production and co-production of fuels and chemicals. In particular, the analysis of an extensive simulation work on biomass to liquid fuels is presented for the comparison between process model results and the corresponding mass and energy targets.