Kinetic modelling of polythionic acids in Wackenroder reaction

The Wackenroder reaction, which consists in the liquid phase oxidation of H2S by SO2 to produce polythionates, is at the base of the HydroClaus process, a novel H2S valorization technology patented by Eni S.p.A. In this work, polythionate kinetics in Wackenroder reaction is studied. The influence of operating conditions, i.e., temperature and residence time, on the system has been investigated through experimental data collected in a bench scale reactor. The experimental apparatus behaviour has been assessed by means of a step tracer experiment. As the reacting system is a gas–liquid one, the controlling regime has been identified thanks to a qualitative analysis of the available tests. Due to the very complex nature of the reacting system and the large number of chemical species involved, a single and two-lumped models have been considered to describe the phenomenon. Results show good agreement between the experimental data and the developed model.