CFD Simulation of a Counter-current Spray Drying Tower with Stochastic Treatment of Particle-wall Collision

In this study, a steady state, three-dimensional, multiphase CFD modeling of a pilot-plant counter-current spray drying tower is carried out to study the drying of detergent slurry and to predict spray-dried detergent powder characteristics. The coupling between the two phases is achieved using the Eulerian-Lagrangian approach. The continuous phase turbulence is modeled using the Reynolds stress transport model. The droplet drying kinetics is studied using a semi-empirical droplet/particle drying model. Emphasis is given on the modeling of particle-wall interaction by considering only the rebound effect and specifying the coefficient of restitution as a function of impact angle with wall surface roughness taken into account using a stochastic approach, as well as a function of moisture content. This influences the post-wall collision trajectories of particles, residence time distribution and the overall exchange of heat and mass transfer. The model predictions agree well with the measured outlet values of powder average temperature, moisture content and exhaust air temperature considering the complexity of the process and the measurements accuracy.