Numerical simulation and parameter optimization of milk powder superheated steam spray drying based on DEM-CFD

Spray drying is a critical step in milk powder manufacturing, essential for ensuring product quality and shelf stability. However, frequent particle collisions and agglomeration during drying often lead to wall deposition and other defects, significantly compromising product quality, safety, and market value. To address this issue, this study integrated superheated steam drying with conventional spray drying. Discrete element method (DEM) was adopted to characterize the agglomeration mechanism of milk powder particles. A mathematical model more consistent with the actual drying process was established and numerically solved. Model validation under hot air drying conditions yielded a 9.91% relative deviation between simulated and experimental final moisture contents, confirming the model’s reliability. The drying medium was then replaced with superheated steam to systematically evaluate the effects of inlet steam temperature, air velocity, and drying chamber geometry. Results indicate that excessively low superheated steam temperature or high air velocity reduced the drying rate. Under these conditions, steam readily condenses on cooler particle surfaces, impeding temperature elevation and maintaining high moisture levels. This promotes particle agglomeration and wall adhesion, particularly in the conical section of the dryer. Conversely, increasing the height and diameter of the drying tower effectively reduced the probability of particle agglomeration and wall adhesion. Finally, the optimal parameters determined via simulation optimization are as follows: superheated steam temperature of 493 K, air velocity of 3 m s−1, feed solution concentration of 20%, peristaltic pump rotational speed of 55 rpm, tower height of 1.0 m, and tower diameter of 0.27 m. This study provides a comprehensive analysis of particle agglomeration dynamics and offers structural optimization of the drying tower in superheated steam spray drying of milk powder and provides theoretical guidance for technological innovation and industrial application of milk powder spray drying.