Wirksamkeit von Tunnelwänden als Träger photokatalytischer Oberflächen: Hauptstudie

The aim of this project was the conception and construction of enclosed, photocatalytic reactors (tunnel cassettes) to reduce the nitrogen oxide concentration in the tunnel “Rudower Höhe” in Berlin by 15%. The project was separated in two phases. Phase 1 included the development of an enclosed system with suitable photocatalysts and light sources. According to different investigations and simulations, a tunnel cassette with the dimension of 1.5 x 3 x 4 m³ was designed including three fans with a volume flow of 1,500 m³/h for each fan. For the photocatalytic degradation, 13 foam mats were integrated being coated with a cement-Photoment mixture. As light sources, the fluorescent tubes Philips Cleo Performance 80 were used. Based on simulations, 50 tunnel cassettes are needed on each side in the end of the tunnel for the reduction of the concentration of nitrogen oxide by 15%.
In phase 2, the realization of the tunnel cassettes in the tunnel “Rudower Höhe” was planned. However, the practical application could not be realized because of the failure of a subcontractor being responsible for the production, installation and service of the cassettes. Nevertheless, to demonstrate the functionality of the determined tunnel cassette, the TU Berlin produced a demonstrator tunnel cassette by itself and carried out a test mode for a longer period. Concerning the photocatalyst, the problem occurred that the photocatalytic degradation decreased due to ageing.
Furthermore, comprehensive measurements at the tunnel 'Rudower Höhe' were carried out used as basis for the conception of the tunnel cassette. For the evaluation of the photocatalytic materials, measurements according to DIN ISO 22197-1 were used. Furthermore, a special reactor (CST reactor) was designed and constructed for the estimation of the efficiency of foam mats allowing a two-sided UV radiation and the flow of the air through the sample.