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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).

The objective of this study is to develop a model for the description of torrefaction. The model is conceived in the context of process modelling and therefore it aims at providing coherent mass and energy balances of solid and gaseous products, rather than a physical description of the process. The rationale underlying the proposed model stems from the representation of torrefaction and its products on a C–H–O ternary diagram and its focus is the description of the solid product in terms of yield, composition and heating value. The heating value of the gaseous products is determined by considering water, carbon dioxide and acetic acid as the major volatile products and closing the mass balance. It is possible to extend the number of species considered in the torrefaction gases if experimental data regarding the volatile products are available. The proposed model is simple, of easy implementation and calibration, of fast resolution and its results have been validated against experimental data. This work represents the basis for a future evaluation and optimisation of torrefaction as a pretreatment step in the thermo-chemical conversion of biomass.

Synthetic fuels, or synfuels, can be produced from gas, coal and biomass. The conversion of gas and coal is well established but lignocellulosic biomass conversion is slow to develop. This paper addresses the issue of the production cost of second generation biofuels via the thermo-chemical route, biomass to liquids (BtL). Techno-economic studies help identify promising conversion processes, but also introduce a false confidence in the technology that may lead to ill fated decisions. A large number of techno-economic studies have been published since the year 2000 showing a large variability in the results. This paper analyses the published data and presents causes of the observed variability, including a comparison with coal and gas to liquids. Large uncertainties remain however with regard to the precision of the economic predictions. It will be shown that the spread in the economic source data accounts for much of the spread in the predictions. These uncertainties affect both CtL and BtL cost predictions. It will be shown however that the results are relatively coherent and that most of the differences between the costs of synthetic fuels can be traced back to economies of scale considering mature technology. (C) 2014 Elsevier Ltd. All rights reserved.

In a carbon and resources constrained world, thermo-chemical conversion of lignocellulosic biomass into fuels and chemicals is regarded as a promising alternative to fossil resources derived products. Methanol is one potential product which can be used for the synthesis of various chemicals or as a fuel in fuel cells and internal combustion engines. This study focuses on the evaluation and optimization of the thermodynamic and economic performance of methanol production from biomass by applying process integration and optimization techniques. Results reveal the importance of the energy integration and in particular of the cogeneration of electricity for the efficient use of biomass.

Pyrolysis experiments were performed between 800 degrees °C and 950 degrees °C on wood particles with diameters from 350 to 800 $\mu$m in a lab-scale drop tube reactor to reproduce surface heat flux representative of gasifiers conditions. It was shown that particle size affected the required pyrolysis time but changed neither gas/tar/char mass yields nor composition of the products at the end of pyrolysis. The initial particle size also affected the resulting char morphology: the larger the biomass particles, the more fibrous the char. Temperature had influence neither on gas/tar/char mass yields nor on gas and solid elemental composition at the end of pyrolysis, but significantly changed the yields of individual gas species. Whatever the conditions tested, a significant shrinkage could be observed on particles during pyrolysis. These experimental results confirm the strong coupling between chemical reactions, particle geometrical properties and heat transfers during pyrolysis under these conditions.

Biomass gasification at temperatures below 1273 K produces gas which contains methane and too much tar for Fischer–Tropsch synthesis. The aim of this study is to investigate methane conversion at high temperature. Experimental tests were performed between 1273 and 1773 K, with a mixture of gas representative of wood pyrolysis at 1100 K (main components only: CO, CO2, CH4, H2, H2O). Two different kinetic schemes were used to predict the gas composition, and PAH molecules formation. For a residence time of 2 s in the reactor, the gas must be heated to at least 1650 K to reach a methane conversion rate of 90%. A parametric study was performed at 1453 K, by varying the initial methane, steam and hydrogen contents, so as to find out which components are the most influent on methane conversion and soot production.

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.

International audience; Modelling approaches of biomass steam gasification are investigated that take into account both chemical and physical kinetic limitations. The gas phase can be described by two independent reactions: (i) the steam reforming of CH$_4$ , which is kinetically limited under the operating conditions (1073 < T < 1273 K, p = 1 bar), (ii) the water-gas shift reaction, which would be close to equilibrium under the operating conditions (1073 < T < 1273 K, p = 1 bar). Concerning solid, a time scale analysis of the main phenomena has been performed. For particles of 500 lm, the transformation can be seen as two successive steps: (i) pyrolysis of biomass, which is both chemically and heat-transfer controlled; (ii) steam gasification of residue, which is chemically controlled.

The use of renewable energy sources is becoming increasingly necessary to diminish the greenhouse effect gases production. Biomass is the most common form of renewable energy, widely used in the third world. Pyrolysis, which corresponds to the thermal decomposition of biomass under the action of heat and without any oxidant, is particularly well-adapted to the valorisation of lignocellulosic products such as wood or straw. The BIOCARB programme of the Commissariat a l'Energie Atomique (CEA), to which the Groupe de Recherche sur l'Environnement et la Chimie Atmospherique (GRECA) contributes, aims to produce carburant from the gasification of biomass. This fuel can be either pure hydrogen, or gasoil produced by the Fischer–Tropsch process after the pyrolysis and syngas production. It is absolutely necessary to control the different parameters of the pyrolysis (gas composition, formation of tars) to maximise the production of hydrogen or syngas. The new coefficient of pyrolytic valorisation presented here helps to meet this requirement. This work presents also experiments on the pyrolysis of straw and fescue in a 550–650 °C temperature range with different residence times, on which was based our investigation.

This work addresses the integrated design of the High Temperature Steam Electrolysis (HTSE) and Biomass to Liquid (BtL) hybrid process. The comprehensive gate-to-gate analysis includes BtL and hydrogen production on-site operations. Simulations are carried out using commercial process simulation software – ProSimPlus® – to allow physical modeling as well as mass and energy balances; modeling is based on standard elementary and user modules and supported by various CEA (French Atomic Energy and Alternative Energies Commission) previous works. The framework for assessment is proposed. Considering productivity, efficiency, cost and environmental issues, five sustainability criteria are chosen: carbon matter yield; energy efficiency; greenhouse gas emissions; electrolysis water use; levelized biofuels production cost. Simulations results verify that hydrogen input is almost doubling the biogenic carbon conversion into liquid biofuels. They bring out significant secondary energy saving for HTSE compared to standard process; and clear advantages over alkaline electrolysis considering technical and environmental criteria. HTSE coupling allows a sharp increase in productivity (biofuels/biomass) with a limited increase in cost and environmental impacts at almost constant primary efficiency.

International audience; Second generation biofuels offer a key for several energy issues, but feedstock is still limited. To improve the use of biogenic carbon, coupling Biomass to Liquid (BtL) process to a hydrogen supplier unit is studied. Water electrolysis enables to produce hydrogen and also required oxygen in line with energy issues; High Temperature Steam Electrolysis (HTSE) coupling is particularly promising: it allows to recover free heat from BtL process and to reuse coproduced water, offering therefore synergies. This work addresses the integrated design of the HTSE and BtL hybrid process for its optimization. The comprehensive gate-to-gate analysis includes BtL and hydrogen production on-site operations. Considering productivity, efficiency, cost and environmental issues, five criteria have been chosen: carbon matter yield; energy efficiency; greehouse gases emissions; water use; levelized biofuels production cost. Simulations are carried out using a commercial process simulation software - ProSimPlus® - to allow physical modeling and mass and energy balances; modeling is based on standard elementary and user modules and supported by various CEA previous works. The first concluding elements in studying integrated HTSE-BtL process verify that hydrogen input is almost doubling the productivity (biofuels/biomass). They bring out significant secondary energy saving for HTSE compared to standard process; and clear advantages over alkaline electrolysis considering technical and environmental criteria. The framework for design optimization is proposed.

International audience; In order to optimize H2 and CO production from biomass gasification, the thermal decomposition of methane in a reconstituted syngas was investigated in a tubular reactor at 130 kPa, for a gas residence time of 2 s and as a function of temperature (1000-1400 °C), CH4 (7, 14%), H2 (16, 32%), and H2O (15, 25, 30%) initial mole fractions. H2 showed an inhibiting effect on CH4 conversion whereas H2O had few effects. Three detailed elementary mechanisms were used to predict the methane conversion rate and to identify the key reaction pathways. Flow rate analyses showed that carbon oxidation occurs mainly by addition of OH radicals on C2 compounds. OH radicals are mainly produced by CO2 (CO2 + H ) CO + OH). The inhibiting role of H2 on CH4 conversion is explained by a competition between the OH radicals consumption channels (H2 + OH ) H2O + H). The competition between thermal conversion of methane and reforming of unsaturated C2 explains the soot formation.

International audience; Experiments are performed in an entrained flow reactor to better understand the kinetic processes involved in biomass pyrolysis under high temperatures (1073–1273 K) and fast heating condition (>500 K s−1). The influence of the particle size (0.4 and 1.1 mm), of the temperature (1073–1273 K), of the presence of steam in the gas atmosphere (0 and 20 vol%) and of the residence time (between 0.7 and 3.5 s for gas) on conversion and selectivity is studied. Under these conditions, the particle size is the most crucial parameter that influences decomposition. For 1.1 mm particles, pyrolysis requires more than 0.5 s and heat transfer processes are limiting. For 0.4 mm particles, pyrolysis seems to be finished before 0.5 s. More than 70 wt% of gas is produced. Forty percent of the initial carbon is found in CO; less than 5% is found in CO2. The hydrogen content is almost equally distributed among H2, H2O and light hydrocarbons (CH4, C2H2, C2H4). Under these conditions, the evolution of the produced gas mixture is not very significant during the first few seconds, even if there seems to be some reactions between H2, the C2 and tars.

The objective of this paper is to address the issue of the production cost of second generation biofuels via the thermo-chemical route. The last decade has seen a large number of technical–economic studies of second generation biofuels. As there is a large variation in the announced production costs of second generation biofuels in the literature, this paper clarifies some of the reasons for these variations and helps obtain a clearer picture. This paper presents simulations for two pathways and comparative production pathways previously published in the literature in the years between 2000 and 2011. It also includes a critical comparison and analysis of previously published studies. This paper does not include studies where the production is boosted with a hydrogen injection to improve the carbon yield. The only optimisation included is the recycle of tail gas. It is shown that the fuel can be produced on a large scale at prices of around 1.0–1.4 € per l. Large uncertainties remain however with regard to the precision of the economic predictions, the technology choices, the investment cost estimation and even the financial models to calculate the production costs. The benefit of a tail gas recycle is also examined; its benefit largely depends on the selling price of the produced electricity.

Bioenergy II : fuels and chemicals from renewable resources, March 8-13, 2009, Rio de Janeiro, BRAZIL; International audience; In the present work, a drop tube reactor (DTR) and a horizontal tubular reactor (HTR) were used to study the pyrolysis behaviour of beech wood particles of different sizes under the conditions encountered in industrial fluidized bed gasifiers, namely high external heat flux (105-106 W.m 2) and high temperature (800-1000 C). The influence of the reactor temperature (800 and 950 C), of particle size (from 350 µm to 6 mm), and of gas residence time (from 1 to 10 s) were examined. Under the explored conditions, when pyrolysis is finished, more than 80 wt.% of virgin wood is converted into gas and less than 13 wt.% remains in solid. In the gas phase, CO is the main gaseous product (50 wt.% of virgin wood), followed by H 2 (molar ratios of H 2 /CO are between 0.35 to 0.55), H 2 O, CO 2 and CH 4. Species C 2 H 2 , C 2 H 4 , C 2 H 6 and C 6 H 6 are present in much lower amounts. The increase of temperature increases the rate of solid devolatilization and favours the cracking reactions of hydrocarbons. The increase of particle size increases the required time for completing pyrolysis. Meanwhile, the results obtained at 950 C show that the final products distribution at the end of pyrolysis is almost the same for the particles between 350 and 800 µm. The increase of the particle size from 800 µm to 6 mm seems to have some influence on the final products distribution. The gas phase reactions mainly change the yields of light hydrocarbons and H 2 : the increase of gas residence time favours the cracking reactions of hydrocarbons and thus leads to a higher H 2 yield.

This paper addresses the techno-economic evaluation and optimisation of processes converting lignocellulosic biomass into liquid fuels, through the development of a suitable framework and the modelling and design of Biomass to Liquids (BTL) processes. In particular, the focus is on the production of drop-in fuels through gasification and Fischer–Tropsch (FT) synthesis. Several conversion technologies are presented and evaluated in the literature, but the comparison of different options is hazardous because of the different assumptions and methodologies adopted in each study. A systematic and consistent approach is therefore developed to explore the trade-offs of alternative process configurations and of the operating conditions. The comparison presented in this study explores the trade-offs of different technological options in terms of competing economic and thermodynamic objectives. Results show that for 200 MWth biomass input plant capacities, production costs are in the range of 1.0–1.4 € l−1 for technologies producing up to about 0.5 kJFT kJth−1 and close to being neutral in terms of electricity balance. For technologies using electrolysis the conversion can increase to 0.8 kJFT kJth−1 with production costs of 1.8 € l−1. The electricity storage capacity, in this case, is of 0.5 kJe kJFT−1, corresponding to a net electricity requirement of about 0.4 kJe kJth−1.