Sorption behavior of four tropical woods using a dynamic vapor sorption standard analysis system

Sorption behavior of four tropical woods coming from Cameroon is studied using a Dynamic Vapor Sorption-Intrinsic apparatus. Sorption isotherms at 20°C and 40°C of Triplochiton scleroxylon (obeche), Entandrophragma cylindricum (sapele), Sterculia rhinopetala (lotofa) and Terminalia superba (frake also called limba) are compared to those in the literature with methods using saturated salts for lotofa and frake with satisfactory results. Experimental values are fitted using two sorption isotherm models. Sorption hysteresis is greatest in sapele and least in frake. When temperature increases, differences in the hysteresis of sorption among the woods decreases. Hystereses of all studied woods ranged from 0,5 to 3%. Our studied woods have lower equilibrium moisture content probably caused by the higher values of extractives content. The water sorbed molecules on multilayer during both adsorption and desorption at 20°C and 40°C is greater in the case of frake and lower in the case of lotofa. The water sorbed molecules on multilayer of sapele is greater than those of obeche. The predominance of multilayer over monolayer of our woods is from 0,2 to 0,4 relative humidity in adsorption phase, and from 0,3 to 0,4 relative humidity in desorption phase

Modeling and simulation of an industrial indirect solar dryer for Iroko wood (Chlorophora excelsa) in a tropical environment

This paper presents a modeling of an instrumental indirect solar wood dryer less expensive functioning in a Cameroonian climate applied to the climate of Yaoundé. The dryer is easy to build and electric energy is only used for the fan. Applications are done on Iroko wood (Chlorophora excelsa), a tropical wood 50mm thick most utilized in Africa. A satisfactory agreement between experimental and numerical results was found. Influences of thickness, wood initial water content and airflow rate were studied

Characterization of sorption behavior and mass transfer properties of four central africa tropical woods: Ayous, Sapele, Frake, Lotofa

This study provides the sorption isotherm, its hysteresis and their mass transfer properties of four Central Africa Tropical woods widely used for building construction: frake (Terminalia Superba), lotofa (Sterculia Rhinopetala), sapele (Entandrophragma Cylindricum) and ayous (Triplochiton Scleroxylon). Characterization of these four species in particular and Central Africa tropical woods in general were necessary to develop conservation and treatment of wood after first transformation using the drying. Also, moisture transport on wooden material used such as wall buildings can be facilitating to found the thermal comfort. Measurements of isotherms were performed using a dynamic vapor sorption apparatus (Surface Measurement Systems) at 20 and 40°C with air relative humidity ranged from 0% to 90%. Mass diffusivity was determined in steady state using a specific vaporimeter. Air permeability was determined using a specialized device developed to measure over a wide range of permeability values. Permeability and mass transfer properties were determined in the tangential direction with a ‘’false’’ quartersawn board (sapele and lotofa) and in the radial direction with a flatsawn board (ayous and frake). Samples of sapele, ayous and frake are heartwood when lotofa contains as well as heartwood than sapwood. Results obtained showed that the temperature effect on sorption behavior was quite low. We observed also a low difference between the sorption behavior of these different species and hysteresis of sorption decreases when temperature increases. Hailwood-Horrobin model’s explains plausibly the experimental sorption isotherms data. Results on characterization of mass transfer properties showed that, in the steady state, mass diffusivity decreases exponentially when basal density increases. Mass diffusivity was higher in desorption than in adsorption phase. The gaseous permeability of these species was between than those of Australian hardwoods and temperate woods. It was difficult to define a relationship between permeability and mass diffusivity

R&D en Lorraine pour la conversion thermique de la biomasse

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Nitrogen Removal from Wood Laminated Flooring Waste by Low-Temperature Pyrolysis

International audienceThe optimisation of wood laminated flooring decontamination was studied to improve energy recovery. This work addresses the first step of a novel nitrogen-containing biomass waste-to-energy process that has been previously published. Pyrolysis in N-2 atmosphere performed at different temperatures (523-673 K) and different durations led to the removal of nitrogen contained in the material, mainly in the forms of ammonia (NH3) and isocyanic acid (HNCO), as analysed by Fourier Transform infrared spectrometry. The optimisation of this step consists in determining a [temperature, duration] of treatment parameters couple to obtain a maximum nitrogen removal coupled with the minimum energy loss in the residue. Amounts of removed nitrogen were determined through ultimate analysis, and energy available in the ``decontaminated'' residues was obtained by calorimetry. Pre-treatment at 548 K during 11 min appeared to be the most promising, with 65 % of nitrogen removed and mass and energy losses of 18.7 and 8.9 %, respectively

Elaboration d'un système de dépollution adapté aux appareils de chauffage domestique au bois

Les contextes climatique et énergétique mondiaux encouragent les pays de l'Union Européenne à améliorer leurs impacts environnementaux. Un des objectifs consiste à diminuer les émissions de CO2 en développant les énergies renouvelables. En France, la filière bois énergie représente la première source d'énergie renouvelable avec une production s'élevant à 10 MTep par an. Toutefois, il est indispensable de ne pas se limiter aux émissions de CO2 pour déterminer l'impact global d'une source d'énergie. En effet, la combustion de bois dans les appareils de chauffage domestique tels que les poêles, les inserts, les foyers ouverts, est à l'origine d'une part non négligeable de certains polluants atmosphériques tels que le CO, les COV, les HAP et les particules fines. L'objectif de ce projet est de réaliser un système efficace de dépollution capable de traiter l'ensemble des polluants à la sortie de ces appareils de chauffage. Des technologies sont déjà disponibles pour la dépollution des fumées issues de différentes sources de combustion, néanmoins nous devons intégrer les problématiques liées au fonctionnement de ces appareils ainsi que des critères de coût, de fonctionnalité et de développement durable définis dans un cahier des charges réalisé avec le partenaire industriel. Le travail réalisé nous à permis de concevoir et de tester un système complet capable de traiter tant les composants gazeux à l'aide d'un catalyseur à base de fer imprégné sur de la cérine, que les particules grâce à un lit filtrant régénéré par microondes. Le système décrit dans ce manuscrit présente une réduction faible des émissions, mais a permis de mettre en lumière les contraintes et les espoirs d'un futur système de traitement efficient.The global energy and climate contexts encourage EU countries to improve their environmental impacts. One goal is to reduce CO2 emissions by developing the use of renewable energies. In France, wood is the first renewable energy source with an equivalent of 10 Mtoe produced each year. However, it is essential to study the global environment impact of on this energy source including CO2 emissions but also the different pollutants emitted. Indeed, the combustion of wood in small home heating units as stoves, open and closed fireplaces, is responsible for a significant part of typical air pollutants such as CO, VOCs, PAHs and fine particles. The objective of this project is to develop an effective system able to treat both pollutants emittedfrom those heaters. Few technologies are already available for smoke after treatment. However, we must incorporate in our study constraints related to the operation of these wood heating devices as well as criteria of cost, functionality and sustainability defined in the specifications set with the industrial partner of this project. The result of the work performed in this project was the conception of a complete prototype tested for emissions reduction. The system is composed of ceria impregnated iron catalyst for gaseous compounds oxidation and a microwave regenerated bed filter for particles elimination. The tests performed on the prototype showed weak emissions abatement. Nevertheless, this project highlighted constraints and hopes for a future efficient after treatment system.STRASBOURG-Bib.electronique 063 (674829902) / SudocSudocFranceF

Procédé multi-étagé de valorisation de déchets bois type panneaux de particules

L étude présentée dans ce manuscrit s inscrit dans les contextes environnementaux de la production d énergie renouvelable et de la valorisation des déchets à base de bois. Il s agit de valider et d optimiser un procédé multi-étagé pour les déchets bois de type panneaux de particules. Dans ces déchets le bois est généralement associé à des résines urée formaldéhyde et mélamine formaldéhyde, composés riches en azote qui conduisent à la production de gaz polluants (ammoniac, acides isocyanique et cyanhydrique, NOx ) lors de leur valorisation énergétique (combustion, pyrolyse, gazéification). Le procédé proposé vise dans un premier temps à éliminer l azote contenu dans le déchet pour produire un solide de type bois chauffé ou charbon dont la valorisation est envisagée dans un second temps par différents voies. La première étape consiste en une pyrolyse basse température (250C à 400C) pendant 3 à 15 minutes et permet d éliminer environ 70 % de l azote initial pour les différentes conditions étudiées. Le traitement à 250C permet d obtenir un meilleur rendement en solide et donc énergétique. La pyrolyse et/ou la pyrolyse / gazéification à la vapeur d eau du résidu de la première étape sont ensuite étudiées entre 800C et 1000C. Le niveau de température le plus élevé assure le meilleur rendement gazeux et permet de produire un gaz riche en hydrogène et en CO utilisable dans divers procédés de valorisation énergétique. La pyrolyse / gazéification permet de convertir l ensemble du solide carboné optimisant ainsi l efficacité énergétique du procédé. En revanche, la simple pyrolyse du solide conduit à une production de gaz moins importante mais permet de piéger une part de l azote dans le charbon résiduel final. Celui-ci, après une étape d activation, semble particulièrement bien adapté au piégeage par adsorption du phénol et des composés aromatiques en phase liquide. Ainsi, les travaux effectués montrent qu un procédé multi-étagé est une voie intéressante pour valoriser des sous-produits bois à faible coût en leur donnant une forte valeur ajoutée.Within the environmental contexts of power generation and waste disposal, the present works deals with the validation and the optimisation of a multistage thermo chemical process of particleboard waste conversion (enhancement). These wastes are mostly associated with urea formaldehyde and melamine formaldehyde resins which contain a huge amount of nitrogen. Nitrogen causes the production of pollutants such as ammonia, isocyanic acid, cyanhydric acid and NOx during classical thermo chemical process (combustion, pyrolysis and gasification). The process studied aims in a first time to remove nitrogen species from waste to produce a combustible solid and in a second time to convert this residual solid in a combustible gas. The first step consists in a low temperature pyrolysis (250C to 400C) during 3 to 15 minutes and assumes to eliminate 70 % of the initial nitrogen content for all studied conditions. The pyrolysis and/or the pyrolysis / gasification under water of the residue are then studied between 800C and 1000C. The higher temperature of reaction (1000C) improves the production of gases and the energy efficiency of this second step and allow the production of hydrogen and carbon monoxide rich gases. The pyrolysis / gasification under water allows a total conversion of the solid which optimises the energy efficiency of the process. However, the pyrolysis under nitrogen produces a lower amount of gases but helps to catch a part of the nitrogen in the residual char. The char then produced is converted through an activation step, in an active char containing nitrogen functionalities with high adsorption capacities, especially for the trapping of phenol or other aromatic compounds in liquid phase. This multistage is thus a interesting way to enhance low cost raw matter like particleboard waste.NANCY1-Bib. numérique (543959902) / SudocSudocFranceF

Modeling and simulation of the drying of beech timber (Fagus Sylvatica) using oscillating regimes

International audienceThis paper represents a numerical study of the massive (60mm) and thin (38mm) wood drying using oscillating drying regimes applied on beech timber (Fagus sylvatica). All thermo-physical properties relative of studied wood are taken from the literature on appropriate experiments. We showed that Luikov's model can be used to predict temperature and moisture content evolutions using oscillating regimes. First numerically tests on 60mm timber wood consists in increasing and decreasing alternation of the drying parameters (temperature), at the rising 12-15°C and at the descent 10-12°C, every alternation being higher than the precedent with 2-4°C. Second numerical test consists to oscillate the values of equilibrium moisture content with the oscillation amplitudes of ±10% and ±20% at the frequencies of 6hours. These practical experiments are detailed in the literature. Luikov's model gives satisfactory results, according to the experiments obtained in the literature. But, convective transfer coefficients are function of each experiment and we observed a short difference between oscillation amplitudes of ±10% and ±20% on moisture content evolution. Thus, Luikov's model can be a tool to study oscillation drying timber in order to reduce consumption of energy during the drying process

Etudes expérimentales des transferts de masse et de chaleur dans les parois des constructions en bois, en vue de leur modélisation. Applications aux économies d'énergie et au confort dans l'habitat

Les matériaux hygroscopiques, et tout particulièrement le bois et ses dérivés possèdent des propriétés complexes rendant difficile la modélisation des transferts couplés de chaleur et de masse dans les parois incluant ces matériaux. De ce fait, très peu d'outils numériques sont aujourd'hui capables de prédire correctement la performance hygrothermique de l'habitat bois. L'objectif de ce travail est de caractériser expérimentalement les transferts chaleur-masse dans les parois des constructions bois afin de valider un outil numérique destiné à simuler le comportement hygrothermique des parois comportant des matériaux hygroscopiques. Dans un premier temps, les notions théoriques et les études antérieures sur les transferts couplés chaleur - masse sont présentés. Ensuite, nous donnons un descriptif détaillé du dispositif expérimental conçu pour caractériser les transferts couplés chaleur-masse dans les parois. Les expériences de caractérisation des performances hygrothermiques des parois fournies par les industriels partenaires du projet TRANSBATIBOIS dans lequel s'inscrit cette thèse sont également abordées. Nous détaillons par la suite les expériences réalisées ainsi que la phase de confrontation des résultats expérimentaux avec les résultats prédits par le code numérique BuildingPore et l'outil commercial WUFI. La troisième partie de ce travail est consacrée aux expérimentations à l'échelle de l'enveloppe. Nous y présentons une analyse de la performance hygrothermique et des consommations énergétiques des constructions bois à travers le suivi de modules-test exposés au climat extérieur. La dernière partie du travail est consacrée aux dispositifs de suivi de bâtiments.Coupled heat and moisture transfer through hygroscopic materials, particularly wood and wood-based products are difficult to model. This is partly due to some specific and complex properties of these materials that are often not included in numerical models. Currently, only a few numerical models are able to predict accurately the hygrothermal performance of wooden building envelope. The aim of this work is to assess the heat and moisture transfer in wooden building envelope through experiments and validate the prediction capacity of a numerical model developed to simulate hygrothermal behavior of envelope including wooden materials. After giving a theoretical reminder of the coupled heat and moisture transfer through building envelope and reporting the results of previous studies in this field, we will give details of the experimental investigation on heat and moisture transfer through timber walls. Firstly, the experimental apparatus used for the wall tests is presented. Then, we will analysis the hygrothermal performance of wooden walls provided by the partners of the TRANSBATIBOIS project in which this work was achieved. Experimental works achieved for Buildingpore model validation and results of the comparisons between experimental assessment and numerical predictions with Buildingpore and WUFI are also reported. The third part of this study deals with the experimental assessment of wooden building envelopes exposed to climatic conditions. An analysis of the hygrothermal performance and the energy consumption of wooden test-cells is performed and reported in this part. The latest part concerns experimental works on buildings.METZ-SCD (574632105) / SudocNANCY1-Bib. numérique (543959902) / SudocNANCY2-Bibliotheque electronique (543959901) / SudocNANCY-INPL-Bib. électronique (545479901) / SudocSudocFranceF