What Are The Limitations Of A High-Speed Disperser?

The limitations of high-speed dispersers are product rheology dependent. That means much has to do with the flow characteristics of the product being dispersed. If it is too thick, it will not move freely to and from the blade from the wall of the tank—hence dead zones of undispersed materials in the tank. If it is too thin, there may not be sufficient body to generate tearing between the layers of product as they consecutively contact the rotating disc. Tacky or “sticky” products may also hinder the blade’s ability to generate proper flow within the tank. Proper flow should resemble a doughnut, with the blade acting as the hole. Product should flow in a circumferential pattern around the tank wall while simultaneously rolling inward to contact the blade. This type of flow is sometimes referred to as a “doughnut roll.” If undispersed particles stick to the walls of the tank or the flow is insufficient to roll the entire dispersion into the blade, a thorough dispersion is unachievable. Without flow, there is no “go.”

Adding supplementary agitation to help feed the high-speed disperser blade can extend the operating range of a disperser. This type of machine is typically called a dual or triple shaft mixer. It has a shaft with a slow-moving sweeper blade passing close to or scraping the tank wall to promote mass flow, and one or more additional mixing shafts with disperser blades to generate high-shear.