Numerical Study and Experimental Validation of Skim Milk Drying in a Process Intensified Counter Flow Spray Dryer

Abstract

This research presents 3D steady-state simulations of a skim milk spray drying process in a counter-current configuration dryer. A two-phase flow involving gas and discrete phase is modeled using the Eulerian–Lagrangian model with two-way coupling between phases. The drying kinetics of skim milk is incorporated using the Reaction Engineering Approach. The model predictions are found to be in accordance with the experimental temperature measurements with a maximum average error of 5%. The validated computational model is employed further to study the effects of nozzle position, initial spray Sauter Mean Diameter (SMD), air inlet temperature, and feed rate on the temperature and moisture profiles, particle impact positions, drying histories, and product recovery at the outlet. The location of the nozzle upwards (≈23 cm) resulted in maximum product recovery and increased the mean particle residence time at the outlet. A similar trend was observed for the highest feed rate of 26 kg/h owing to the increased spray penetration upstream in the chamber. The maximum evaporation zone was detected close to the atomizer (0–10 cm) when the spray SMD is 38 µm, whereas it shifts upstream (40–50 cm) of the dryer for an SMD of 58 µm. The high air inlet temperature resulted in enhanced evaporation rates only in the initial 10–20 cm distance from the atomizer. The results obtained in this study are beneficial for the development of the novel vortex chamber-based reactors with a counter flow mechanism.

Employing the H-type finned heat exchangers with the circular tube for energy-saving purposes of the spray dryers

“…Caused of these applications, different research has been performed to clarify several aspects of this process [11][12][13][14][15][16][17][18][19][20][21]. Caused of the considerable energy consumption by the spray dryers [22][23][24], decreasing their energy usage by different approaches like heat recovery has been the subject of several works [25][26][27]. Golman and Julklang [28] investigated various options that can be utilized for heat recovery in spray dryers.…”

On the heat recovery of the spray dryers by using the tube-finned heat exchanger with elliptical holes

“…The spray dryers are considered as energy intensive operations that consume a large portion of the applied energy to the industrial unit [22][23][24]. Hence, proposing an approach to reduce the energy consumption or recover the exhaust heat from the spray dryer has been the subject of some research [25][26][27].…”