Multiphase Euler–Lagrange CFD simulation applied to Wet Flue Gas Desulphurisation technology

The gas and liquid hydrodynamics inside an Open Spray Tower has been simulated using a commercial CFD code, while a model that treats the absorption process of SO2 has been developed and implemented in the software through dedicated modules. Besides SO2 absorption also evaporation of slurry droplets and droplet-wall interaction are considered, the latter modeled with an empirical correlation and implemented in a sub-module. The continuous gas phase has been modeled in an Eulerian framework, while the dispersed liquid phase with a Lagrangian approach by tracking a large number of particles through the computational domain. Physical absorption of SO2 has been modeled using dual-film theory and appropriate empirical and semi-empirical correlations. The model for aqueous phase chemistry considers instantaneous equilibrium reactions of eight dissolved species into a slurry droplet, namely: SO2aq, CO2aq, H+, OH-, HSO3-, SO3--, HCO3-, CO3--. The empirical droplet-wall interaction model handles impact, deposition and splashing events occurring when a liquid particle hits an internal element of the scrubber. A pilot plant OST has been simulated and the numerical results show good agreement with the experimental values of pressure drop, temperature and sulphur dioxide removal efficiency.