Fachdokumente Online der Landesanstalt für Umwelt Baden-Württemberg

zur LUBW   zum Ministerium für Umwelt, Klima und Energiewirtschaft   zum Ministerium für Ländlichen Raum und Verbraucherschutz   zum Ministerium für Verkehr und Infrastruktur  

Summary

Exhaust air streams coming from technical processes can contain breathable oxidable aerosols. The reliable entire removal of those aerosols often still represents a farreaching unsolved problem. The possible aerosols vary in a wide spectrum. Examples are sootable emissions from combustion engines, wood stoves, roast- and smoke processes and breathable dusts from wood-, textile-, plastic-, and food-processing plants and bioaerosols of various nature and origin (aerosols from biological sewage cleaning plants as well as germs of diseases, pollen and other allergic aerosols esspecially in hospitals and clean room areas.) In this project the total oxidation of these aerosols to CO2, water and anorganic residue substances has been investigated.

The heat intgration when oxidizing arosols is very important because of aerosols released from processes above show only little concentration of pollutants and come up usually at low temperatures. Big air streams must be heated up to a reaction temperature while the amount of the reaction heat released by the oxidation of the particle is small. For that purpose a counter flow reactor for oxidizing aerosols has been developed and optimized, which is distinguished by a high heat integration[1]. The significance of this concept is the internal heat exchange between the entering and the escaping air.

In the reactor exhaust air and purified air flow alternating in neighbouring channels. The channels are provided with corrugated structures to attain a high rate of heat transfer.

For this several structures were developed and the local heat transfer coefficents were determined and optimized for them. Through the use of suitable structures it is possible to reduce the size of the appartus by a factor of 12 in comparison with deploying only flat channels. For the design of the reactor a simulation of the operating behaviour by a mathematical model of the reactor was prepared. In various calculations the operating behaviour was determined. For examination of the catalytic and the thermic oxidation of aerosols several counter flow reactors with different geometries of the channels were developed and constructed. Experiments were performed for the developed counter flow reactors oxidizing various types of aerosols. Types of aerosols used were: smoke aerosols, aerosols of wooden dust and a bioaerosol from yeast. For the generation of these aerosole models several aerosol generators were developed and constructed. The conversion behaviour of these aerosols in a counterflow reactor had been examined under several working conditions. The examinations verify that organic aerosols in a counter flow reactor can be practically completly converted. This is valid for the examined aerosols from wooden dust as well as for the examined smoke aerosols. In that case the contained smoke particle as well as the volatile organic compounds in the smoke aerosols oxidize practically complete. Also odouring substances contained in the smoke aerosole can be converted by a rate higher than 99%. As an example for the removal of bioaerosols from waste air an inactivation of a yeast aerosole had been examined. The experiment proves the possibility of a dry sterilisation of air streams in a counter flow reactor. The distinct advantage of a counter flow reactor lies in the very high rate of internal heat exchange. Because of this the inactivation is possible at low energy expenses.

 


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