Abstract
The electron beam technology has been developed successfully for the removal of sulphur and nitrogen oxides from flue gases and has recently been applied on an industrial scale. The flue gases contain also nitrogen, carbon dioxide, oxygen, water, and ammonia. As the sulphuric acid appears during the chemical processes generated by the beam interactions with the gas phase components, it starts reacting with water, both condensing as fine liquid droplets (nucleation), where other components of the flue gas are absorbed. The chemical processes extend to the liquid phase as reactive extraction of components like SO2, HNO3, HNO2, O2, and NH3. The rate of the latter is influenced by both the gas to liquid mass transfer and the thermodynamic equilibrium instantaneously established at the gas-liquid interface. To the best of the authors’ knowledge, this approach proposes the first complex mathematical model which includes the concomitant chemical processes in the gas and liquid phases, as a way to better understand the electron beam flue gas treatment mechanism. The flue gas was assumed to be irradiated over a period of 12.6 s at 1 atm and 60 °C with a dose of 10 kGray. The kinetics, involving 139 chemical reactions, were assembled from various sources, and integrated into a first principles based mathematical model, consisting of a system of 70 unsteady-state mass balance equations. Dissociation of the absorbed component into ionic species was also modelled, according to the appropriate mass and charge balances. The results are in satisfactory agreement with published data from industrial and laboratory scale experiments.
