| Environnement, ingénierie & développement |  |
N°15 - 3ème Trimestre 1999
1. Éditorial n°15 Déchets Sciences et Techniques
Dans le précédent numéro (n° 14), Serge Lambert évoquait, avec des documents d'archive à l'appui, le rôle des fumées d'usine dans la publicité au temps des « pollutions bienfaisantes ». Cela m'a rappelé qu'il m'avait confié, il y a quelques mois, les copies de numéro de L'Illustration en date du 26 mars et du 21 mai 1898, qui relatait des débats techniques au sein du Conseil municipal de la ville de Paris. On y découvre avec étonnement, à propos des ordures ménagères, que des traitements comme le broyage, l'action de la vapeur, l'incinération, voire même la distillation agitaient déjà le microcosme des « rudologues » et je ne peux résister à l'envie de vous inciter à lire les quelques paragraphes ci joints.Cette lecture aura au moins le mérite de nous rappeler avec quelle prudence il faut utiliser des mots comme « innovation », « procédé révolutionnaire »,... qui trop souvent accompagnent notre développement technologique dans l'ignorance de l'histoire des sciences. On y découvre aussi à quel point était ancrée la volonté de valorisation des déchets ou bien encore la faible part des préoccupations sanitaires au cœur de nos débats actuels. Les chiens posaient aussi des problèmes aux responsables municipaux, mais à l'époque il s'agissait des « chiens errants ».
2. L’avenir des emplois du déchet : le cas des ordures ménagères
Household refuse: the future of the employment.The paper synthesizes the results of a research for Région Rhône-Alpes, in relationship with Institut national de génie urbain de Lyon - Agence des Villes.The objective is to consider the possibilities of change concerning the jobs: do the new jobs, particularly in the frame of the development of separate collection of household waste, modify the content of the traditional jobs? Is de-compartmentalization possible?
3. Analyse comparative des filières d'oxydation des boues de stations d'épuration urbaines
ln this paper different municipal sewage sludge oxidation technologies (mono-incineration and mono-gasification, co-incineration in hard coal-fired power plants, waste incineration and gasification plants, and cement furnaces, aqueous phase oxidation) are compared taking into account related atmospheric emissions, energy efficiency and costs. A global evaluation based on these criteria reveals that the co-incineration in hard coal fired power plants incorporates the highest energy efficiency and the lowest overall costs. Its main disadvantage in comparison to mono-incineration, mono-gasification, and co-incineration in municipal waste incineration plants refers to elevated mercury emissions related to the sludge input. The problem of elevated mercury emissions is even more serious in the case of co-incineration in cement furnaces. However, the installation of fabric filters downstream cement furnaces may reduce mercury emissions significantly.
4. Valorisation de la coquille du cabosse (Theobroma cacao L.) et des boues agroindustrielles comme support dans la fabrication des inocula pour légumineuses
This study evaluated the survival of Rhizobium leguminosarum bv phaseoli strain in agro-industrial and agricultural waste carriers. Shells of cacao pod, Fermex (Fermentaciones Mexicanas S.A. de C.V.) waste sludges, and their combinations with Mexican peat were compared with Mexican peat and imported peat. Ali carriers sterilized by two successive autoclavings at l20°C for 1 hour before being inoculated. Broth culture of rhizobia with a total count of 2x109 cells/ml was added to the milled supports. After thorough mixing the carriers were packed into sealed polyethylene bags. The bags were storeded at 4°C for six months.Plate counts of viable cells of rhizobia were determinated in the carrier materials at 1, 30, 63, 141 and 176 days. Survival of rhizobia was found to be very good in the carrier made of the combination of cacao pod shells and Mexican peat. After six months, viable cell concentration in this combination was comparable to that found in the imported peat (around 3,8x109 cells/g). Survival in Fermex waste mud was also good (around 2x109 cells/gram). The Mexican peat showed a fair survival whith only 5,3x108 cells/g, below the recommended population of l,0x109. The other carrier tested (cacao pod shells alone, shells plus Fermex sludge, and Mexican peat plus Fermex sludge) did not show any viable cells after six months.
5. Traitement des gaz d'incinération par voie sèche : comparaison de deux absorbants à haute réactivité
High reactive lime, similar to Spongiacal, and sodium bicarbonate performance for acid gas removal was compared in the Municipal Solid Waste lncinerator Rémival in Reims. Results show that:- Spongiacal can easily be handled in a unit designed to treat with sodium bicarbonate;- lime consumption is about 25% lower than sodium bicarbonate for the same acid gas removal;- the residus production is 10 to 15% higher with lime compared to sodium bicarbonate;- the most stringent norms ( 10 mg/Nm3 of HCl and 50 mg/Nm3 of SO2) can be reached with an overconsumption of 25%, compared to the current norms (respectively 50 mg/Nm3 of HCl and 300 mg/Nm3 of SO2).
6. Valorisation du biogaz par moteur à allumage commandé : Une approche méthodologique du dimensionnement
The size of an electric power plant using biogaz has to be achieved by the development of a model designed to integrate fuel quality and quantity evolutions throughout life duration of the power plant. A description by “grey box” for the biogaz combustion in spark ignition engines allows to estimate the electric power output. The biogaz composition is featured by “typical days”. The investment decision is generally based on economical criteria, the electric trade, the investment and the maintenance costs are introduced. Results show the optimal power output to install according to the available biogaz flow-rate. The “bottom price” for the electric power, which is the minimum price beneath such a project can not make any profit, is presented.
7. Étude expérimentale de la pyrolyse et de la combustion du polyamide-6,6 à haute température
During the incineration of nitrogen containing polymer wastes such as polyamides and polyurethanes, many nitrogen containing atmospheric pollutants are emitted. However, there is a lack of data on ammonia and nitrogen oxide or hydrogen cyanide formation during the high temperature thermal degradation of this kind of compounds. In order to determine the mechanisms of thermal decomposition of such materials, we studied the pyrolysis and the combustion of nylon-6,6 as a function of residence time and temperature. During pyrolysis, the temperature exhibits a significant influence on the hydrogen cyanide formation and has only little influence on the quantity of NH3 emitted. With an excess of oxygen, we didn't found any more these two species. Whatever the operating conditions, nearly 10% of the fuel-nitrogen is converted into NO and 90% into N2.
8. Caractérisation minéralogique, hydraulique et mécanique des Refiom: Influence de la composition des Refiom sur leurs propriétés
This paper presents first, a characterisation of the unhydrated material « MSWI Fly Ash », and a study of its hydraulicity and hardening. Then it approaches a study on the influence of the variation of MSWI Fly Ash composition on these properties. This second phase of the study is lead by using artificial ash and with the Statistical Design of Experiment Methodology. Elements of comprehension about observed phenomena are also presented in this paper.