Study On Liquid Addition Under Vacuum Post Pelleting Of Feed

The paper reviewed the development of technology and equipment of liquid addition. The advantages and shortcomings of liquid coating were analyzed. If liquid ingredients were added after heat processing, such as feed conditioning, extruding, expanding and pelleting, the loss of heat-sensitive components can be reduced. However, in the traditional liquid coating system, most of the liquid ingredients are coated onto the surface of pellets, some feedstuff fall off the pellets to form powder during the following package and transportation due to rubbing and bumping among pellets, and nearly 80% of the added ingredients were in the fines, so some active components were lost. In the vacuum coating system, the liquid ingredients can diffuse into the inner portion of the feed pellets by pressure gradient after the pressure equalization from the vacuum, the liquid homogeneity between inner portion and outer portion of pellet increases, so the loss of effective components decreases.A new vacuum coating system was designed by analyzing the features of current liquid coating system . A special mixing device was developed by improving the traditional rotation mixer, the best mixing time was shorten ,and the homogeneity was improved. The effects of mixing time, diameter of the spray nozzle, pressure of liquid spraying and vacuum pressure on the uniformity of coating were studied by the element tracing method. In the meantime, the result indicated that the rate of active resolve increased greatly by liquid coating.The homogeneity between the inner portion and outer portion of pellet was studied for the first time. Many major factors that can effect the homogeneity of pellet were discussed. The effects of the diameter of pellet, the amounts of liquid added, the vacuum equalizing rate, the vacuum pressure were studied by adding liquid Vitamin B1. The results indicated that smaller pellet sizes, higher level of liquid, shorter time of vacuum equalizing and lower vacuum pressure can improve the homogeneity between the inner and outer of pellet. At last, the effect of adding plant oil under vacuum was also studied.