DEM-CFD simulations and PIV/PTV experiments on charging of pneumatically conveyed powders

As the world population increases, the demand for food increases as well. This urges the production of (enriched) food to become more energy efficient in order to have a sustainable situation. A possible approach is to switch to separation techniques that do not require water. One such a method is tribo-electric separation where the driving force for separation is the different polarity and/or magnitude acquired by different fractions due to contact charging (also known as tribo-electric charging or tribo-electrification). Contact charging occurs always when objects of different material touch; the magnitude and polarity is a property of the combination of the two touching materials. Consequently, the method is suitable to separate mixtures in which the components have sufficiently different charging characteristics. Many configurations are possible to utilize contact charging to charge powders. Here we investigate pneumatic conveying of powder through a metal duct; while traveling through the duct, particles will hit the walls and acquire charge. As the experimental set-up is such that optical access is possible, Digital Image Analysis is performed on the duct. From this, the particles’ spatial distribution in the duct can be determined. The results show the same trend as predicted by our simulations.