Euler–Lagrange simulation of slurry droplet evaporation in spray drying using a kinetics-based drying model

This paper presents a numerical model to describe the evaporation and drying of liquid droplets containing dissolved solids, relevant to processes like spray drying and spray pyrolysis in the food and pharmaceutical industries. A one-way coupled Euler–Lagrange approach is developed, where the gas flow inside the dryer is addressed in the Eulerian framework while the droplet dynamics and motion are tracked using the Lagrangian framework. In the Lagrangian framework, a novel and detailed kinetics-based multi-stage drying model is developed. The droplet level model is validated against experimental data for skim-milk droplet drying, showing strong agreement. Effects of different activation energy models are also analyzed and it is found that one model predicts the drying characteristics better than the other. Finally, large-scale three-dimensional simulations are performed on a lab scale spray dryer drying Maltodextrin solution in water. It is demonstrated that the model correctly predicts variation in final particle size distribution due to changes in drying air characteristics, paving way for the deployment of the model in predicting final particle characteristics in a spray dryer.