Three-Dimensional Spray-Drying Model Based on Comprehensive Formulation of Drying Kinetics

In our previous 2D axisymmetric study of the spray-drying process, it was shown that the introduction of comprehensive formulation of drying kinetics had a substantial influence on both predicted gas and particle flow patterns in a spray dryer. On the other hand, it was demonstrated that the concept of 2D axisymmetric modeling is suitable for fast and low-resource consumptive numerical calculations of the spray-drying process and that the predicted velocity, temperature, and vapor mass fraction are of reasonable accuracy. However, due to their restrictions, 2D axisymmetric simulations fail to predict asymmetry of flow patterns and the presence of the transversal air flow and cannot provide actual 3D representation of particle trajectories inside the spray chamber. Therefore, in the present study a novel 3D theoretical model of multiscale multiphase transport phenomena in a steady-state spray-drying process is proposed for predicting more realistic particles paths, residence times, temperatures, and moisture contents. A drying process of silica slurry in a short-form pilot-scale spray dryer fitted with a pressure nozzle atomizer is investigated. The simulated 3D drying behavior of the dispersed phase and flow patterns of air velocity, temperature, and humidity are compared with the previously published results of 2D axisymmetric modeling. A significant influence of both drying kinetics and number of utilized dimensions on the predicted particle trajectories and transport phenomena in the drying chamber is observed. Hence, a proper formulation of the droplet drying kinetics and realistic 3D flow modeling is crucial for accurate numerical representation of the actual spray dryer performance.