Modeling of maltodextrin drying kinetics for use in simulations of spray drying

This study investigates the drying kinetics of maltodextrin droplets using experimental and numerical methods. Single droplet drying experiments, conducted under controlled conditions (air velocity 5 cm/s, air humidity 5 g/kg) using the filament method, aim to determine the critical moisture content for surface locking of droplets (initial diameter 1200 − 1600 µm). The experiments examine how this critical moisture content varies with initial solids content of the droplets (20–40% w/w) and air temperature (80–120 °C). A spatially resolved single droplet drying model (complex model) is adapted and validated, showing excellent agreement with experimental drying curves. This model is then employed to simulate conditions more representative of spray drying. A parametric study assesses the influence of air temperature (60–240 °C), initial droplet diameter (30 − 500 µm), and air velocity (0.01–5 m/s) on drying rates, highlighting the interplay among these variables. For these conditions, the complex model is finally reduced to a characteristic drying curve model whose computational simplicity makes it suitable for implementation in computational fluid dynamics simulations of spray drying. To further improve the model predictions and account for the influence of process conditions, an extension modulating the model parameter n (ranging from 0.88 to 1.62, with a median of 1.07) is proposed.