A modelling framework for bulk particles dissolving in turbulent regime

A mixing-tank model combining CFD simulation and Noyes–Whitney equation has been demonstrated for predicting dissolution of spray-dried detergent powder. The dissolution behaviour of bulk particles has been directly linked to the input power of the mixing system which is highly desired by industry with the aim of reducing testing when extrapolating particle dissolution performance from bench scale measurements to any washing system/condition. Initial particle parameters such as density, solubility, size distribution and diffusivity were considered. The model was first validated with experiment of non-porous single-ingredient particle Na2CO3 granules. Later, porous multi-ingredients particles from spray-drying pilot were used to validate the model with dissolution experiment data. The good agreements between experiment and simulation at different agitating speeds and temperatures illustrated that the model can be used for predicting bulk particles dissolving in a turbulent regime where they are well suspended in the mixing system. The CFD simulation results revealed detail information about energy dissipation rate across the vessel which explained the phenomena that when non-porous Na2CO3 granules were not well mixed in the system, dissolution predicted by modelling was much faster than experiment, indicating that local energy dissipation rate could be one solution to improve the modelling accuracy of this case.