Effect of torrefaction on grinding energy requirement for thin wood particle production

National audienceThe second generation biofuels exploits the lignocellulosic materials. The main advantage is to not compete with food chain. In the case of thermochemical means (gasification in an entrained flow reactor followed by Fischer-Tropsch synthesis), a grinding step is necessary to inject particles into the burner. The targeted particle size is about 200µm to reach a total conversion and to improve gas quality. Due to the plastic behaviour of the biomass, this step is strongly energy-consuming. Biomass torrefaction (thermal treatment lower than 300°C) is a way to decrease the grinding energy and to standardize materials (composition and moisture). Contrary to natural wood, torrefied wood has a brittle behaviour and a less mechanical strength. The aim of this study is to investigate the interest of torrefaction on wood grinding energy diminution. The torrefactions were carried out on beech and spruce, in an airtight rotating batch kiln under nitrogen. The effect of torrefaction temperature (160-300°C) and duration (5-60min), on weight loss, grinding energy and powder particles size were examined. The grinding energy was calculated by integration of the electric power of the grinder, which was measured by the means of a wattmeter. A grindability criterion, which took into account both grinding energy (E) and the volume fraction (X) of particles lower than the targeted size (200µm), was defined. Results showed a strong interest of torrefaction on the decrease in energy required for fine wood particle grinding. The grindability criterion could be reduced by 93% for treatments beyond 260°C. However, the global energy balance becomes less favourable. It is necessary to reach a compromise between the consumed energy by torrefaction and the decrease in grinding energy. According to the wood species, an optimum could be established around 10% of weight loss and around 85% of the grindability criterion diminution

9. Bioraffinerie

La bioraffinerie est une raffinerie dans laquelle les procédés de transformation sont non seulement de nature biologique mais aussi physique et chimique. Le préfixe « bio » ne se justifie donc que par le caractère vivant de la matière première : la biomasse. La bioraffinerie est en concurrence avec la raffinerie pétrolière quand elle est capable de proposer au marché des molécules analogues dans leurs propriétés et dans leurs usages. Bioraffinerie traditionnelle Dans leur version traditionnel..

Une Revue des Approches Expérimentales pour Analyser les Modes d'Endommagement et les Performances Balistiques de Céramiques pour Blindage

At: ENSAIT (Ecole Nationale Supérieure des Arts et Industries Textiles)International audienceDuring the three last decades several testing configurations have been developed to investigate the dynamic behaviour and damage modes in armour ceramics under high-strain rates loading conditions. The edge-on impact configuration and the pyrotechnic spherical expansion experimental method can be used to investigate the tensile damage and microplasticity mechanisms in ceramics at strain-rates ranging from 103 s-1 to 105 s-1. The Hugoniot Elastic Limit and the spall strength of ceramics can be analysed by means of plate-impact experiments or highpulsed power technologies (GEPI testing facility). The tandem configuration that consists in impacting a ceramic target previously subjected to an impulsive load aims at characterising the strength of a pre-fragmented ceramic under the impact of a penetrating projectile. In the present work, the principle of each testing configuration and the main results obtained with SiC ceramics are introduced. The main observed damage mechanisms and the obtained dynamic response are explained. These experimental data allows identifying a constitutive model of ceramic to be used in a numerical simulation describing the ballistic impact of an AP projectile against a bilayered configuration. This numerical approach is necessary to highlight the state of loading applied to the ceramic front plate and to deduce which are the main mechanical properties involved in the ballistic performance of armour ceramics

Biofuels in the nexus energy-environment-food

The production of biofuels from biological resources has been the subject of much controversy. Their opportunity update deserves to be revisited for technological maturity and assess their relevance in response to current environmental concerns.Innovations in biotechnological and chemical processes allow a wide range of liquid and gaseous biofuels; their characteristics concern energy content, compatibility with fossil fuels and openness towards strictly chemical uses.The factors driving this technological market's evolution are the implementation of abundant public policies, the evolution of agronomic practices, the concern for carbon sequestration in soils, the expectations of the aeronautical sector with biokerosenes, and consumer behaviours. From field crops and forests, the mobilizable raw materials have been extended to microalgae, animal, households and plant wastes. Biofuels are then part of the territorial bio-economy and the circular economy. Value chains are more complex than those traditionally focused on biodiesel based on oilseeds and sucrose from beet, cane or starch from wheat or maize. The integration of economic actors and the scaling of markets have been the subject of foresight work at international and French levels. Environmental sustainability is generally proven, with reservations for some sources (soya, oil palm). Biofuels are part of a food-energy-environment nexus. Public policies, if based on the sustainability and social acceptability of biotechnology, will also guide the choices of economic interests alone. This article discusses the research and development work needed to make biofuels a sustainable part of energy policy.La production de biocarburants à partir de ressources biologiques a fait l’objet de nombreuses controverses. Leur opportunité mérite d’être revisitée pour la maturité technologique et évaluer leur pertinence en réponse aux préoccupations environnementales actuelles. Les innovations dans les procédés biotechnologiques et chimiques permettent une large gamme de biocarburants liquides et gazeux; leurs caractéristiques concernent le contenu énergétique, la compatibilité avec les carburants fossiles, l’ouverture vers des usages strictement chimiques. Les facteurs d’évolution de ce marché technologique sont l’implantation de politiques publiques foisonnantes, l’évolution des pratiques agronomiques, la préoccupation de séquestration du carbone dans les sols, les attentes du secteur aéronautique avec les biokérosènes, et les comportements des consommateurs. A partir des plantes de grande culture et des forêts, les matières premières mobilisables se sont élargies aux microalgues, aux déchets animaux et végétaux. Les biocarburants s’inscrivent alors dans la bioéconomie territoriale et l’économie circulaire. Les chaines de valeur sont plus complexes que celles anciennes centrées sur le biodiesel à base d’oléagineux et de saccharose de betterave, de canne ou d’amidon de blé ou de maïs. L’intégration des acteurs économiques et le dimensionnement des marchés ont fait l’objet de travaux de prospective aux échelles internationales et francaises. La durabilité environnementale est avérée globalement avec toutefois des réserves pour certaines sources (soja, palmier à huile). Les biocarburants s’insérent dans un nexus alimentation-énergie-environnement. Les politiques publiques, si elles se fondent sur la durabilité et l’acceptabilité sociale des biotechnologies, orienteront aussi les choix des seuls intérêts économiques. Cet article aborde les travaux de recherche et développement nécessaires pour inscrire durablement les biocarburants dans les politiques énergétiques

Global warming and the collapse of theFrench Guiana shrimp fishery

This paper studies the biological and economic effects of globalwarming on the French Guiana shrimp fishery. The sea surface tem-perature is explicitly introduced into four natural growth functions,among which the Cobb-Douglas function best adjusts the availabledata. Besides, a Cobb-Douglas harvest function is also estimated, in-dicating that shrimp production in French Guiana is highly sensitive tothe shrimp stock, which implies that global warming may have strongeconomic implications. We nally consider a centralized resource man-agement of the French Guiana shrimp shery, that is undertaken invarious trend scenarios concerning the sea surface temperature. Un-der the most plausible scenario, in which the sea surface temperaturefollows the trend of the last decades, prots and biomass respectivelydecrease and collapse around the end of the 2020s

Maximum Economic Yield Fishery Management in the Face of Global Warming

International audienceThis paper deals with fishery management in the face of the ecological and economic effects of global warming. To achieve this, a dynamic bioeconomic model and model-based scenarios are considered, in which the stock's growth function depends on the sea surface temperature. The model is empirically calibrated for the French Guiana shrimp fishery using time series collected over the period 1993–2009. Three fishing effort strategies are then compared under two contrasted IPCC climate scenarios (RCP 8.5 and RCP 2.6). A first harvesting strategy maintains the Status Quo in terms of fishing effort. A more ecologically-oriented strategy based on the closure of the fishery is also considered. A third strategy, which relates to Maximum Economic Yield (MEY), is based on the optimisation of the net present value derived from fishing. The results first show that ‘Status Quo’ fishing intensity combined with global warming leads to the collapse of the fishery in the long run. Secondly, it turns out that the Closure strategy preserves stock viability especially under the optimistic climate scenario. Thirdly, the MEY strategy makes it possible to satisfy bioeconomic performances requirements with positive stock and profit, once again, especially under the optimistic warming scenario. Consequently, MEY emerges as a relevant bioeconomic strategy in terms of adaptation to climate change but only in connection with climate change mitigation