Improvement of Flowability of Fine Cohesive Powders by Flow Additives

Most minerals and concentrates, auxiliaries, agricultural and synthetic particulate solid products are produced with particle sizes of less than 100 μm. These fine powders show similar problematic product properties. Their interparticle adhesion forces, especially van der Waals forces, exceed the gravitational forces by orders of magnitude. Thus, the trouble-free treatment of these products presents large problems as well as scientific and technological challenges. The physical properties of such materials, especially flowability, are essential for many industrial applications including product generation, processing, application and consumption, e.g., in the pharmaceutical, chemical, food and manufacturing industries or plant engineering. In recent decades, one of the most frequently used solutions to this problem has been to add small amounts of flow additives that improve the flowability of these fine cohesive powders. This paper provides an overview of the physico-chemically active principles of flow additives, model approaches and useful flowability evaluation methods. The efficiency of several flow additives, i.e., nanoparticles and surfactants, is critically discussed by the provision of selected test results from the literature. Conclusions are drawn with respect to the application of this flow additive method in process industries.