(173b) Falling Film UV-Reactor Design
Photochemical reactions and photochemical treatment of hazardous substituents have become a high priority agenda in recent years. Waste water treatment and air pollution control with Advanced Oxidation Processes are subject of research. Different technologies and reactor systems are used. To enable investigation of a variety of different constituents a flexible reactor design based on falling film absorption has been developed. Investigation of absorption processes in falling film columns in laboratory scale has several advantages. It is possible to investigate mass transfer because of well defined mass transfer area. The apparatus used in this project has an active height of 1.25 m. It can handle liquid phase volumetric flow rates of 20 to 200 l/h and gas flow rates of 0.1 to 15 m³/h. For investigation of irradiation enhanced absorption processes a 700 W Hg medium pressure source and a 120 W Hg low pressure lamp can be installed in the centre of the falling film column. For quantitative specification of the setup performance the radiation intensity can be locally measured with a spectrometer. The integral photon flux is determined with a chemical actinometer. The apparatus arrangement allows investigation of gas phase reactions, the combination of photochemical reactions in the gas phase and in the liquid phase, and photochemical liquid phase reactions. At the present status practical application has been investigated with radiation supported SO2-absorption and NOx-absorption with radiation supported chemical reduction in the liquid phase. In both applications operation in the bubble column mode is recommended because SO2 might cause formation of sulphuric acid aerosols during radiation supported oxidation in the humid gas phase and in radiation supported NOx-absorption with chemical reduction in the liquid phase NO2-cleavage in the gas phase has a negative effect on absorption efficiency.