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• A CFD model of powder spraying in modified Wurster apparatus was developed. • The model was validated using a digital PIV method. • The Euler–Lagrange approach using the discrete phase model (DPM) was applied. • The model enabled the prediction of air-powder mixture movement in the device. • The powder velocity was mainly determined by the spouting airflow rate. The aim of these studies was to examine the suitability of the Euler–Lagrange approach for modelling the powder spraying process performed with a pneumatic nozzle used for dry coating in spout-fluid bed apparatus. Simulation results were validated using the digital PIV (Particle Image Velocimetry) method and measurement equipment constructed by the authors. The validation process led to the determination of the optimal Ansys Fluent solver settings, which ensure a satisfactory accuracy of the simulation results (the average relative error of all simulation points at the level of 10.5%). The experimental results are most accurately reflected by simulation results obtained with the use of the standard k − ε model that has the discrete random walk (DRW) model activated. The detailed analysis of the operation of the spout-fluid bed apparatus allowed for the examination of the influence of hydrodynamic parameters (the mass flow rate of the gas spraying the powder and plasticizer, as well as spouting gas) on the velocity and concentration of the dispersed phase in the device. The scientific investigation covered the analysis of the velocity profiles and the volume fraction of the coating powder in different zones of the column. [ABSTRACT FROM AUTHOR]

Highlights • The CFD model is used for the description of liquid atomization. • Impact of the model parameters on the calculated droplets velocity is investigated. • The secondary phenomena have the greatest impact on the droplets velocity. • The results are compared with our own experimental data. • The calibrated model is used to describe the plasticizer atomization. Abstract The aim of this study was to develop a CFD model for initial qualitative analysis of the operation of the pneumatic nozzle used for dry coating. The calibration consisted in comparing the droplets velocity yielded by the model with our own experimental data. The impact of the sheet and ligament constants as well as of the application of secondary coalescence and breakup models on dispersed phase velocity were taken into consideration. It turned out that the secondary phenomena had the largest impact on the dispersed phase velocity. Only after they had been taken into consideration was the agreement between the computation results and empirical data satisfactory. Afterwards, the best set-up of the model was used for describing the plasticizer atomization in a draft tube of a spout-fluid bed apparatus. It was concluded that this process should be carried out with the atomizing gas at a pressure of 2 ∙ 105 Pa. [ABSTRACT FROM AUTHOR]