| Environnement, ingénierie & développement |  |
N°67 - Juin 2014
1. Éditorial n°67 Déchets Sciences et Techniques
Chères lectrices, chers lecteurs, Vous tenez entre les mains un ouvrage que je vous recommande de conserver jalousement plusieurs années. Non pas pour contribuer à réduire le volume de déchets dans nos poubelles, ni pour étudier la stabilité bio-physico-chimique du papier dans le temps sous l'effet de facteurs d'influence environnementaux, mais parce qu'il va devenir un objet de collection ! Ce numéro de DST est en effet probablement le dernier qui sera publié sous format papier. A partir du prochain numéro, nous envisageons une diffusion exclusivement numérique de la revue.
2. Lavage des sables contaminés par les hydrocarbures en colonne à lit fluidisé : Approche expérimentale
In this work, a method for washing sand contaminated by petroleum is described. It consists in extracting the pollutant from the soil grains using fresh water without any chemicals. Two sets of experiments were conducted: at small scale using test tubes and at large scale using one fluidizing column. Experiments with test tubes were performed in batch mode using dune sand of 312 µm mean diameter artificially contaminated with petroleum at an amount of 10% based on clean sand weight. The study of the effect of many operating parameters on decontamination efficiency has shown that water temperature and agitation intensity exerts remarkable effects. On the contrary, initial contaminant concentration and treatment duration exerts just little effects. Experiments using fluidising column were performed using the same contaminated sand in continuous mode. Sand grains were fluidised by ordinary water at a sufficiently low velocity to avoid any entrainment. Temperature was kept at 50 °C. Results showed that fluidisation is an efficient technique in view of high yield of petroleum recovery (up to 65% in mass). The absence of any chemical additive to water makes this operation both cheap and ecological.
3. Etude de mise en place d’un tri sélectif à l’université de Mohammedia, Maroc
The present research work is a contribution to the decision-making support in the management of domestic and assimilated waste produced by Hassan 2 University in Mohammedia. It supplies the reference data on the composition and the flow of production waste then identifies the various constraints (institutional, legal, financial, technical and/or educational), which limits the implementation of a continuous management and the establishment of a selective collection to the source. Besides, it allows us to determine the sustainable solutions and to propose an approach of development of this service.Therefore, we conducted five days for the collection and sorting of waste generated by the various institutions, which showed that the university is one of the largest producers of waste, (3900 euros are spent for the collection and processing of 113 tons each year). Also, the study exposed that the University household waste contains more than 60.70% of fermentable waste fully recyclable by simple methods, and 30.26% of reusable materials (glass, plastic, paper / cardboard, and metal).
4. Épuration des biogaz par adsorption en vue d’une valorisation énergétique en pile à combustible de type SOFC
Biogas is mainly composed of methane and carbon dioxide, but it also contains trace compounds detrimental for SOFC application. It is therefore necessary to remove these contaminants from the biogas. Three pollutant families have been identified: sulfur-containing compounds, volatile organic silicon compounds (VOSiCs) and chlorinated compounds..In this paper, lab-scale adsorption tests were performed on synthetic polluted gas to evaluate the performance of a polishing treatment to remove hydrogen sulfide (H2S – sulfur compound), octamethylcyclotetrasiloxane (D4 – VOSiC) and cis-1,2-dichloro-ethene (C2H2Cl2 – chlorinated compound). Four kinds of adsorbents were tested: an activated carbon (AC), a silica gel (SG), a zeolite (Z) and an impregnated activated carbon (IAC). Adsorbed quantities and breakthrough times were greatly dependent on the adsorbate/adsorbent couple. On the one hand, SG was the most efficient adsorbent for D4 removal, with an adsorption capacity of 216−259 mgD4/gSG. On the other hand, Z and AC seemed more appropriate for C2H2Cl2 removal, with adsorption capacities higher than 41 mgC2H2Cl2/gAC and 50 mgC2H2Cl2/gZ. Z was also the best adsorbent for H2S removal on dry gas, with an adsorption capacity higher than 133 mgH2S/gZ. The influence of the bed height on H2S and D4 adsorption performance was studied. Competition phenomena were also investigated for pollutants in mixture.
5. Développement de l’écologie industrielle à Madagascar : valorisation de cendre volante dans la construction du béton
The proximity of quarries on the National Highway N° 5 and the Fly ash tailings of the SHERIIT Nickel project coal power plant in the Toamasina region is favorably promoting an eco-industrial synergy for the local production of concrete using fly ash with cement. Material studies showed good physical and mechanical properties for the quarry aggregates according to the P18-541 standards while high SO2 and Fe2O3 proportions and low proportion in CaO as well as a strong specific Blaine area were observed with the fly ash. Mechanical tests showed that the strength of the 10% fly ash-substitued concrete was higher than with 28 day age CPA cement. Moreover, by addition, fly ash is a good plasticizer agent for concrete without any drying shrinkage and with improved handling and strength at 28 days. Hence, workable concrete with excellent mechanical strength can be obtained from cheap materials for real applications.
6. Évaluation du potentiel biométhanogène de biomasses lignocellulosiques
In the selection for renewable energy resources, the bioconversion of biomasses rich in lignocellulose in methane is one of the most promising alternatives. However, the selection of the resources depends not only on their availability but also on their organicphysico-chemical characteristics. Their structure, their composition and the presence of unwanted fractions have consequences on their bioconversion in methane. In this study, the global characteristics (total organic matter, water soluble organic matter), biochemical fractionation (soluble fractions, hemicellulose, cellulose and residual fraction) and bioreactivity (measure of the biological et bioréactivité (mesure de la demande biologique en oxygène – oxygen demand BOD28 , and biomethane potential BMP60) were measured on 25 samples.The comparison of the data by the statistical method of principal component analysis (PCA) led to the highlighting of the good linear correlation between the BMP60 and the BOD28, and a reverse correlation with the content in residual fraction LMBO, corresponding to the ligneous fraction of the organic matter. No correlation seems to be able to become established between the PBM and the contents in organic matters (MV, DCO or COT), the water soluble COD (CODSol) and three soluble biochemical fractions, hemicellulose and cellulose. According to our results, the prediction of the biomethane potential requires to select other parameters which would allow to set considering the structural […]