Spray drying modelling based on advanced droplet drying kinetics

A novel theoretical model of the steady-state spray drying process is presented. The model utilizes two-phase flow Eulerian–Lagrangian approach and involves a comprehensive description of two-stage droplet drying kinetics. Such an approach enables prediction of mass, moisture content and temperature profiles within the spray droplets along with flow patterns of the continuous phase. The developed two-stage spray drying model has been incorporated in on Computational Fluid Dynamics (CFD) package FLUENT™ via user-defined functions and utilized for simulation of the drying process in a short-form pilot-scale spray dryer fitted with a pressure nozzle atomizer. The predicted drying behaviour of the dispersed phase and flow patterns of air velocity, temperature and humidity are compared with the data calculated using the built-in FLUENT drying kinetics model. The results of the numerical simulations demonstrate the considerable influence of the utilized drying kinetics model on the predicted heat and mass transfer in the drying chamber as well as the significant influence of particle-wall boundary conditions on the predicted particle trajectories and residence time. Therefore, a proper modelling of the droplet drying kinetics and realistic boundary conditions are crucial for the numerical representation of the actual spray dryer performance.