| Environnement, ingénierie & développement |  |
N°14 - 2ème Trimestre 1999
1. Éditorial n°14 Déchets Sciences et Techniques: La publicité des fumées d'usine ou le temps des pollutions bienfaisantes
En ce temps-là, et il n'y a pas si longtemps, noires fumées d'usine n'étaient pas vice. Bien au contraire, patrons d'usines, ouvriers, cadres et populations qui en vivaient, étaient fiers de ces hautes et nombreuses cheminées laissant échapper, chaque heure, chaque jour, de lourds panaches blancs, gris ou noirs. Et tous, bénéficiaient de leurs odeurs acres, piquantes, toxiques parfois, mais qui le savait ?Certes la ménagère, ma tante, femme de « mineur » à Moyeuvre-Grande près de Metz, n'appréciait pas toujours d'avoir à relaver linges et draps couverts de suie ou de moucherons... Mais la vie près d'une usine était ainsi. Quant à aller se plaindre à l'usine, aucune femme n'y songerait. Pensez donc, son homme, ses fils, oncles et neveux bien sûr y travaillaient ; elle-même n'y faisait-elle pas quelques « ménages » de bureau !
2. Caractérisation minéralogique et chimique de vitrifiats de REFIOM: Importance de la localisation des éléments polluants
According to the law of July 13, 1992, only ultimate wastes can be accepted in class 1 rubbish dumps after July 1, 2002. This has led to studies concerning the stabilization of such wastes. Two types of vitrified waste (vitrifiats de REFIOM) have been studied, each with a different chemistry and mineralogy. This work shows the importance of some crystals that allow a good stabilization of certain polluant elements whereas other phases can lead to an unstable material.
3. Étude de la combustion de produits organiques aromatiques chlorés: Le cas du monochlorobenzène
Chlorobenzene is widely used in chemical processes, and the elimination of this sort of industrial waste by incineration must be carefully done because this chemical species can lead to the formation of a great number of chlorinated aromatic hydrocarbons. Among these molecules dioxines and dibenzofurans are highly toxic. In order to increase our knowledge of the mechanisms which lead to the formation of these species, a study of the pyrolysis and the combustion of chlorobenzene was done. The different reaction products were identified and quantified, and the influence of temperature and oxygen concentration was investigated. The results show that thermal decomposition is highly dependent upon combustion conditions, 80% of the initial chlorine is present as HCl, the remaining fraction is mainly present in solid carbon. A great number of hydrocarbons is formed, benzene, acetylene and methane represent the main part of the carbon mass balance. Experiments performed in rich conditions showed that two cycle aromatic hydrocarbons were formed: biphenyles or naphtalenes chlorinated or not. In some cases, a substantial amount of phenol and chlorophenol was formed even in stoichiometric conditions.
4. Procédé de réduction de la corrosion par le chlore et de l’encrassement des faisceaux de tubes d'usines d'incinération
The solution to the chlorine corrosion and the fouling problems of boiler and heat exchanger tubes in waste incineration plants is given by the use of ICA products. This is mainly based on the injection at the secondary combustion air entrance of a mineral substance called ICA 5000. Beside its corrosion inhibition effect, it yields the protection of the combustion chamber refractory coating, the formation on the heated surfaces of an easily removable ash, an increase of the plant treating capacity, a decrease of the cleaning.
5. Procédé d'oxydation catalytique en voie humide de la pollution organique aqueuse. Traitement de composés organo-azotés
The wet air oxidation process (WAO) is an efficient method for treating wastewaters containing nitrogenous organic compounds, providing that a composite manganese/cerium oxide (7/3 molar ratio) is used as catalyst. This allows to obtain molecular nitrogen, absolutely harmless to the environment.During preliminary tests, it was established that the temperature (about 260°C) and the catalyst concentration are the most important factors to transform ammonia into molecular nitrogen (N-N2), which is the main product while only very limited amounts of nitrites (N- N02-) and nitrates (N- NO3-) appear. In addition, neither manganese nor cerium were leached off in the solution, under the experimental conditions. This composite oxide catalyst is adapted for the direct conversion of organic nitrogen (N-Org) to molecular nitrogen (N·N2), as well as for the conversion of organic carbon (TOC) to carbon dioxide. This was clearly established during the treatment of aliphatic nitrogenous compounds (-alanine, urea) and aromatic ones (aniline, aminophénol). Ammonia nitrogen (N-NH3) is always the main intermediate product and the rate of elimination of organic nitrogen is always rapid with regard to the second reaction step (transformation of N-NHJ to N-N2), which is the limiting one in this process. To account for the results obtained, it was possible to propose a general simple scheme with two main steps for the nitrogen transformation pathway and to determine the kinetic constants. This […]
6. Le tri des ordures ménagères dans les pays en développement: Étude de cas au Brésil
The feasibility and opportunity analysis to build and operate materials recovery facilities (MRFs) in developing countries has to avoid a mimetic concept on the basis of old industrialized countries.Brazil corresponds in fact to an intermediate position of new industrialized country. Eight examples of MRFs or sorting centers of household refuse have been considered. They correspond to various contexts and have specific characteristics.Complementary investigations concern the outlets of the recovery materials and the recycling facilities, the requirements, the processes and the markets.
7. Métaux lourds dans la matière fermentescible végétale d'ordures ménagères marocaines
Lead contents inferior at 6 ppm of dry matter (d.m) of wasted vegetals in garbage of Rabat (Morocco) are less than that given in literature, over 80 ppm d.m. The lead distribution according to vegetals depends on the physiological behaviour. In fact a linear relation between lead, zinc, chromium having low contents in ppm explains the ash content given in percent. Moreover some plants as parsily have a grade of lead approaching the limit of the acceptable concentration for saling according to the rules given by the French higher committee of health.