Nitrogen oxides and sulphur dioxide have an important role in acid rain production. Most flue-gas desulphurisation methods base on limestone scrubbing and concerning NOx abatement SCR technology is state of the art. There is still demand of new processes for low temperature applications or when catalyst poisoning is expected. Especially simultaneous SOx and NOx control is still of high interest.

Photochemical reactions and photochemical treatment of hazardous substituents became increasingly popular in recent years. Particularly in waste water treatment as well as in off-gas purification Advanced Oxidation Processes are subject of investigation. Dependent on the overall kinetics of photochemical reactions different reactor systems are used. To enable treatment and investigation of a broad range of constituents a flexible reactor design like a falling film reactor is chosen in this project where absorption with photochemical reaction of constituents in the gas phase and the liquid phase was investigated.

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 set up allows investigation of gas phase reactions, the combination of photochemical reactions in both the gas phase and the liquid phase, and photochemical liquid phase reactions.

This paper discusses different basic reaction engineering measurements for the analysis of the reactor performance and application for SOx and NOx control is covered. Absorption of SO2 with photochemical oxidation was successfully tested. Dual step liquid phase nitrate reduction with urea was successfully tested too. While irradiation of NO2 in the gas phase will retard absorption efficiency due to cleavage, simultaneous irradiation of SO2 and NOx in the gas phase and absorption leads to different result which will be presented.