| Environnement, ingénierie & développement |  |
N°23 - 3ème Trimestre 2001
1. Éditorial n°23 Déchets Sciences et Techniques: Management environnemental et écologie industrielle : une question de culture et de compétition économique
Parmi les articles que vous trouverez dans les pages qui suivent, l’un a retenu particulièrement mon attention : « Eco ciment, une expérience au Japon d’un nouveau type de ciment permettant le recyclage de déchets », proposé par des auteurs appartenant à l’un des leaders mondiaux de l’industrie cimentière.La publication en français d’un article écrit par des auteurs japonais est très exceptionnelle et mérite d’être soulignée. Mais c’est le contenu qui peut aussi nous surprendre et appeler quelques réflexions. Les auteurs rapportent en effet leur expérience en matière de recyclage de déchets par l’industrie cimentière, qui se démarque très nettement de nos propres pratiques en France.Le gouvernement japonais a aidé l’industrie cimentière à la mise au point de ciments où plus de la moitié des matières premières sont substituées par des résidus d’incinération d’ordures ménagères et d’autres déchets industriels. Le cadre réglementaire, l’économie des filières industrielles et le marché semblent avoir permis la fabrication à grande échelle de ces nouveaux ciments, qui sont promus pour leur haute valeur environnementale, et qui représentent un excellent exemple de réalisation des préceptes de l’écologie industrielle.
2. Masit: Nouvel outil d’évaluation comparative pour technologies durables
Technology, to be sustainable, has to be mare sober, cleaner, and generally more economical, but also more “socially responsible”. However, if the notion of “environment” is integrated into the development of technologies, the notion of durability is still far from being evoked.Bearing this in mind, the Ademe, the CEA, Ecobilan EDF and the IUT of Saint-Denis have to decided to develop the Masit method: “Multicriteria Analysis for Sustainable Industrial Technologies”.Masit has devised an exhaustive “checklist” following six stages: The identification of the process/product couples, the identification of the flow, the definition of the scope of the study, the definition of the system of measurement, the analysis of the process/ product couples and the application. The project as a whole is analysed taking into account seven different points which constitute quite a global approach to sustainable development: the reglementation, the functional, the technical and industrialisation, the environment, the industrial and technological risks, the economical and the social point of view.The method consists of several criteria, and so we have to take into account interactions between these different points of view. This achieved by charting the interactions on a grid.The values allocated to this interaction depend on the problematic faced by the decision maker, the information obtained, the economical and political context, the information obtained, the economical and […]
3. Systèmes d’informations appliqués aux technologies propres : l’outil recyclé
Currently, clean technologies are essential for the depuration or the valorisation of industrial effluents. The accessibility to the information by the industrialists for the choice of the best suitable technologies is the biggest gap to fill. As part of the European project for inter-regional transfer of recycling techniques and clean technologies Recycle, we proposed a computer tool. This software capitalizes the information and constitutes a decision support system for the clean technologies for the effluents coming from the mechanical and surface treatment industries.
4. Les résidus organiques fermentescibles en quête de réhabilitation
In olden days organic (fermentescible, or biodegradable) residues – including the excreta – were considered “friends (ferments) of the earth”, valuables. The farmers were in quest of nightsoil.The 18th and 19th centuries mark the end of the “golden age” of urban night soil. The project of the new city rejects the waste. Hygienists bring to the fore the sanitary risk and attempt to promote an aseptic environment. Moreover, the manure and the urban compost (in spite of improvements of the composting process) have to compete with chemical fertilizers. The decline goes on during the 20th century. Sorting and composting from mixed households’ refuse give a poor quality product, with a shrinkage of the outlets. The old value becomes a source of increasing cost.Today restoring to favour the fallen and exile is a risky challenge. The image of the urban compost is tarnished. The selective collection concerns mainly the “clean and dry” fractions, whilst the fermentescible organics are considered dirty and filthy.However the compost remains “green gold” for some people and one can observe a revival of bioagriculture and products, in relationship with environmental conservation, sustainable development and healthy food. But this last aspect entails some uncertainties and is controversial.
5. « Écociment »: Une expérience au Japon d’un nouveau type de ciment permettant le recyclage de déchets
A new type of cement has been developed in Japan to solve the municipal and industrial waste problem caused by limited availability of landfill sites and also to contribute to the protection of the environment by providing a complete recycling system of wastes that would otherwise be dumped. This new cement is designed to use municipal waste incinerator ash as up to 50% of raw materials. Combustible wastes like waste oil, plastics, WDF(waste derived fuel) also can be used as fuel. This new cement contains the same main components as normal Portland cement (NPC): alite (C3S), bélite (C2S), calcium aluminate (C3A), calcium alumino-ferrite (C4AF) and calcium sulfate. The manufacturing process of the cement is also mostly the same as NPC. Incinerator ash generally contains substances undesirable for cement, such as Cl and a small amount of heavy metals. The metals vaporize in the form of chlorides through the sintering process and are caught as kiln dust in the bag filter. The heavy metals, then are extracted from the dust through the metal recovery process and delivered to a smelter for refining. This makes the cement process a complete recycle system for municipal and industrial wastes. Another type of cement featuring rapid hardening in one hour was also designed. This cement contains 20% of calcium chloroaluminate (C11A7-CaCl2), instead of C3A. These new cements are usually called in Japan « ecocements ».
6. Recherche d’un procédé hydrométallurgique de valorisation des poussières d’aciérie électrique
Production of steel in the electric arc furnace generates a dust by-product containing non-ferrous metals. EAF dusts are classified as hazardous wastes and are disposed in specialised landfills after stabilisation with hydraulic binder. The process studied in the Laboratory of Materials Electrochemistry consists in an hydrometallurgical treatment of waste based on selective leaching of zinc and lead. At first, a leaching is carried out with a chelating agent, the hydrogenonitrilotriacetate anion. The treatment of different EAF dust samples allows the total leaching of ZnO and PbOHCl. In all cases, solubilized iron level does not exceed 3% in mass. The recovery of metals is performed by precipitation of metallic sulphides with Na2S4. Metallic sulphides can be use in their own metallurgy as raw materials whereas the reagent can be recycled in the process. The leaching residues are inert according to the leaching procedure Afnor X31- 210, but contain important amounts of zinc under ZnFe2O4 form. The recovery of this element requires the destruction of the ferrite structure. For this, ZnFe2O4 is treated by FeCl3, 6 H2O at 150 °C. The whole zinc is extracted. Ultimate solid residues, iron concentrated and free from zinc can be oriented towards steel industry.
7. Formulation et validation d’une hypothèse de pollution de l’eau de surface: Le cas du lac municipal de Yaoundé
The municipal lake on which the present experimentation is based, is situated in the administrative district of Yaounde (Cameroon). It receives all types of garbage and untreated muds from the septic pits and a centre of water treatment broken down more than ten years ago. This article presents a method were the satellite image processing, the field investigation and the physico-chemical analysis of water have been combined to determine the pollution status of this lake.
8. Possibilité d’élimination de cations toxiques contenus dans les eaux au moyen d’une zéolithe synthétique NaP
The synthesis is realised by mixing under strong agitation a solution of hydrated sodium aluminate, a solution of sodium silicate and the water. The mixture was then transferred to a polytetrafluoroethylene bottle, which was sealed and rotated in an oven at 100°C for 18 hours. The white crystalline product was filtered off, washed thoroughly with distilled water, and dried. The chemical analysis of the crystal have shown that the zeolite possesses a typical chemical formula: Na5 [(AlO2)5 (SiO2)11]; 11,5 H2O.The water contents were determined as % weight loss in a thermobalance. The zeolite NaP is characterized by a ratio Si / Al equal to 2,2 and a capacity of exchange of 4,7 meq/g.All exchange were determined at 25°C in agitated thermostats (at least for 5 days). The portions of zeolite and solution were then separated for analysis of the two ions. The results of the elimination have shown that the zeolite NaP can reduce clearly the ions Pb, NH4, Cd and Fe. By plotting the isotherms of exchange, one has shown that the zeolite has made proof of the preference for these four ions. On the other hand, it is particularly not selective for the ions Mg, Mn and Ni in comparison with Na. The copper and the zinc have shown a partial saturation of the zeolite that is having to the suitable that some sites of exchange are inaccessible to these two ions. The order observed decreasing selectivity is: Pb2+ > NH4+ > Cd2+ > Fe2+ > Cu2+ > Zn2+ > Mg2+ > Mn2+ > Ni2+For […]