Computational fluid dynamics modeling of the production process of an atomized egg spray dryer

Abstract

The production of eggs in Uganda has been increasing over the years posing a challenge of preserving eggs during times of low or no market. To ameliorate this problem, an at atomized egg spray dryer was developed by the Department of Agricultural and Biosystems Engineering to transform eggs into powder. This was because the existing method of freezing at temperatures of 10oC to 12oC was realized to be inefficient since it can only preserve eggs for a period of two to three months. However, no process operation analysis has been done yet. The objectives of this study were: to optimize the parameters of the production process using Computational Fluid Dynamics simulations, to estimate the evaporation rate and dryer thermal efficiency of the atomized egg spray dryer and also to estimate the equilibrium moisture content at water activity of 0.4 of the produced egg powder. The simulation was run by varying the inlet temperature of air in a range of 100 –180◦C, where the feed pressure, egg feed rate together with the water activity and relative humidity were kept constant at 200kpa, 0.067kg/s, 0.4 and 40% respectively. Optimum operating conditions were found at 5% EMC where an inlet drying temperature of 140 oC, and an outlet drying temperature of 43.4oC were found. At this optimum condition, the evaporation rate and thermal efficiency were estimated to be 0.0284 and 84.0% respectively. Outlet particle temperature was the most significant process parameter that affected the equilibrium moisture content of egg powder. To improve the thermal efficiency of a spray drying process, inlet drying temperature should be increased by regulating the air heater.