Effective Thermal conductivity of divided silica xerogel beds

International audienceApparent thermal conductivity (λ) measurements were made on monolithic silica aerogels and divided low-density xerogels. The objective of the tests on monoliths was to determine the variation of λ with the solid content. Additional compressive tests were also made to follow the evolution of bulk modulus with apparent density, in order to further optimize the solid content of xerogel particles. Divided xerogels were characterized under the following conditions: at ambient conditions (T, P, and relative humidity of water vapor in air), under partial vacuum (from atmospheric pressure to 4 × 10−7 bar) and under different relative humidities. The effect of the divided xerogel granularity on λ has been studied by using different size range and distributions. The results of our studies indicate an optimum particle density at 0.15 g cm−3, and a decrease in λ for samples containing fine particles

Scrap tyre pyrolysis: Are the effluents valuable products?

12th International Symposium on Analytical and Applied Pyrolysis, UNIV VENICE, AULA MAGNA, VENICE, ITALY, OCT 14-18, 1996International audienceScrap tyre pyrolysis under nitrogen is studied at atmospheric pressure with the aim of producing a solid residue to be burned simultaneously with coal dust in a coal burning power plant. The experimental device maintains isothermal conditions. The temperatures of treatment are: 380, 450 and 550 degrees C. Three phases are obtained after pyrolysis: solid, liquid and gas and their composition is studied in relation to the temperature of the thermal treatment. The solid phase (char)-approximately 40% weight of the initial sample (steel free) mostly constituted of carbon, also contains the main mineral matter initially present in the used tyre. The char produced is brittle and has a high burning power which makes it suitable for burning when mixed with coal dust in coal burning power plants. The steel weave is easily separated from the solid carbon residue after the thermal treatment and recovered without physical or chemical change and can be recycled. The gas phase contains a mixture of light hydrocarbons, dihydrogen and carbon dioxide. The IRTF spectra of evolved gases shows a change in the ratio of every gas while the pyrolysis takes place. The liquid phase is a complex hydrocarbon mixture in which some components have been identified. The chemical-valorization of the liquid phase is an alternative to a thermal valorization. The pyrolysis appears to be a technique which is able to reduce a bulky, high polluting industrial waste, while producing energy and/or valuable chemical compounds

Energy valorization of industrial biomass: Using a batch frying process for sewage sludge

Issu de : WasteEng 08 - 2nd International conference on engineering for waste valorisation, Patras, GREECE, June 3-5, 2008International audienceThis paper studies the energy valorization of sewage sludge using a batch fry–drying process. Drying processes was carried out by emerging the cylindrical samples of the sewage sludge in the preheated recycled cooking oil. Experimental frying curves for different conditions were determined. Calorific values for the fried sewage sludge were hence determined to be around 24 MJ kg−1, showing the auto-combustion potential of the fried sludge. A one-dimensional model allowing for the prediction of the water removal during frying was developed. Another water replacement model for oil intake in the fried sewage sludge was also developed. Typical frying curves were obtained and validated against the experimental data

Drying kinetics and heat flux in thin-layer conductive drying

International audienceThin-layer drying by coating of a viscous product on a hot metallic surface is studied from the point of view of heat and mass transfer. An experimental device has been built up in order both to provide and to estimate the heat flux density at the interface between the hot plate and the drying sample. Results are presented for alumina sludge drying. The determination of the interfacial heat flux is obtained from temperature measurements in the metallic plate and the solution of an inverse conduction problem. An analytical direct model is made using the quadrupole formalism and the system transfer function is calculated. The inverse problem is solved using Beck's sequential function specification method. Intrinsic drying kinetics are obtained by an energy balance

Valorisation énergétique de la biomasse et des déchets humides

WasteEng Conference Series "Spéciale Afrique 2009", juillet 2009, Ouagadougou, BURKINA FASOInternational audienceSome categories of biological waste such as sludge or some agricultural and food waste are generally considered as inappropriate for valorization into solid biofuels because of their high moisture content. This paper reviews the technological concepts developed during the past ten years to improve the energy balance of a biowaste-to-industrial biosolid valorization pathway. It shows the influence of the dewatering and drying stages on the overall energy efficiency and thus the actual fossil fuel substitution by using these biofuels.Certaines catégories de déchets organiques comme les boues, cer-tains déchets agricoles ou des industries agro-alimentaires sont généralement considérés comme peu compatibles avec une utilisa-tion en tant que combustibles solides en raison de leur forte teneur en eau. Cet article examine les concepts étudiés au cours de la der-nière décennie, pour améliorer le bilan énergétique d'une filière basée sur la production de combustibles solides à vocation industrielle. Il démontre l'importance de l'efficacité énergétique de la déshydrata-tion et du séchage pour assurer une réelle substitution des combus-tibles fossiles

Apport du couplage d'une thermobalance gravimétrique et d'un analyseur calorimétrique différentiel pour la mesure de l'activité de l'eau dans un mélange liquide solide

International audienc

Bone marrow-derived mesenchymal stem cells drive lymphangiogenesis.

It is now well accepted that multipotent Bone-Marrow Mesenchymal Stem Cells (BM-MSC) contribute to cancer progression through several mechanisms including angiogenesis. However, their involvement during the lymphangiogenic process is poorly described. Using BM-MSC isolated from mice of two different backgrounds, we demonstrate a paracrine lymphangiogenic action of BM-MSC both in vivo and in vitro. Co-injection of BM-MSC and tumor cells in mice increased the in vivo tumor growth and intratumoral lymphatic vessel density. In addition, BM-MSC or their conditioned medium stimulated the recruitment of lymphatic vessels in vivo in an ear sponge assay, and ex vivo in the lymphatic ring assay (LRA). In vitro, MSC conditioned medium also increased the proliferation rate and the migration of both primary lymphatic endothelial cells (LEC) and an immortalized lymphatic endothelial cell line. Mechanistically, these pro-lymphangiogenic effects relied on the secretion of Vascular Endothelial Growth Factor (VEGF)-A by BM-MSC that activates VEGF Receptor (VEGFR)-2 pathway on LEC. Indeed, the trapping of VEGF-A in MSC conditioned medium by soluble VEGF Receptors (sVEGFR)-1, -2 or the inhibition of VEGFR-2 activity by a specific inhibitor (ZM 323881) both decreased LEC proliferation, migration and the phosphorylation of their main downstream target ERK1/2. This study provides direct unprecedented evidence for a paracrine lymphangiogenic action of BM-MSC via the production of VEGF-A which acts on LEC VEGFR-2

L'électromigration appliquée à la dépollution des sols : le cas d'une pollution fluorée

International audienceL'objectif de l'étude est l'application du procédé électro cinétique à l'échelle d'un pilote. Ainsi, une méthodologie est développée afin de définir et de mettre en oeuvre des conditions adaptées à la décontamination d'un sol pollué en fluor par la technique d'électromigration. Tout d'abord, une étude expérimentale est réalisée à l'échelle du laboratoire, afin d'analyser préalablement le rôle de différents paramètres (nature de l'électrolyte uti lisé, granulométrie du sol, gradient de potentiel imposé). Puis, des travaux sont réalisés avec les conditions prédé finies, sur trois échelles différentes (0,8 et 20 litres ainsi que 1,5 m'), afin de mettre en évidence l'impact du changement d'échelle sur les paramètres: quantité de fluor récupérée, durée de traitement, consommation énergétique plus par ticulièrement. The aim of this study is to scale up the electrokinetic process. A methodology was then developed, in order to implement the adapted conditions for the fluorine polluted soil decontamination, by using an electromi gration process. First, a laboratory experimental study was carried out in order to analyse the influence of different parameters (electrolyte type, soil granulo metry, applied electrical potential). Then other studies have been performed, using three scales (0.8, 20 and 1500 litres) to observe the impact of the scale up on the removed fluorine amount, treatment time and the energy consumption parameters