Vacuum Coating of Heat-Sensitive Liquid Ingredients onto Feed Pellets
An experimental vacuum coating system was developed. Liquid vitamin was sprayed into pellets of different 
diameters under vacuum. A special mixing paddle was developed and incorporated into the coating chamber to improve the 
mixing uniformity. The effects of vacuum pressure and spray pressure on the mixing uniformity were studied using the 
methylene violet tracing method. A proper spray pressure needs to be selected to obtain the best mixing uniformity. No effect 
of vacuum pressure on the mixing uniformity among pellets was observed. The effects of liquid dosing, vacuum release time, 
and pellet size on the gradient of liquid concentration between the central and the outer region of pellet were studied. 
Decreasing the vacuum release time reduced the gradient of liquid concentration. Increasing liquid dosing caused a decrease 
of the gradient of liquid concentration. The smaller the pellets, the smaller the gradient of liquid concentration.