Where Do Fines Come From and Why Is Cleaning So Important?
Some dust and contaminants occur naturally in products like minerals, food, tablets and other bulk solids, while others are caused by the way the products are handled. Impurities in plastic pellets, both fines (dust) and angel hair (streamers), are generated by the friction in conveying lines. Dilute phase systems create large amounts of dust and streamers; the higher the velocity, the larger the amount of impurities. Pipe elbows also cause friction and result in the creation of more dust and streamers. The high pressure in dense phase, or slow motion systems, creates very fine dust due to wall friction and friction between pellets. Temperature, pellet shape and product characteristics can also contribute to the creation of dust.
Cleaning bulk solids is important for several reasons. Food and pharmaceutical bulk solids are cleaned for hygienic reasons and to improve the quality of the finished, packaged product. Minerals are cleaned primarily to avoid environmental and health problems. The plastics industry cleans pellets to improve the quality of both the pellets and the finished plastic product.