Impact of Process and Machine Parameters in the Charging Section on the Triboelectric Separation of Wheat Flour in a Vertical Separator

Triboelectric separation has recently been investigated as a novel process for dry enrichment and separation of protein of various crops like wheat flour. The triboelectric effect allows for the separation of starch and protein particles in an electric field based on their different charging behavior despite having a similar density and size distribution. Particles are triboelectrically charged in a charging section before being separated in an electric field based on their polarity. While the charging section is crucial, the influence of process parameters remains largely unexplored. Thus, the influence of the charging sections’ dimensions and the particle concentration as process key parameters was investigated experimentally. Varying the length (0, 105, and 210 mm) showed that the protein shift increases with the length (max. 0.53%) during separation. Varying the diameter (6, 8, and 10 mm) influenced the charging behavior, resulting in an increase in protein accumulation on the negative electrode as the diameter decreased. Varying the mass flow of flour (40, 80, 160, and 320 g·h−1) also affected the separability, leading to a maximum protein shift of 0.61%. Based on the observed results, it is hypothesized that the electrostatic agglomeration behavior of oppositely charged particles is directly affected by alterations in machine parameters. These agglomerates have a charge-to-mass ratio that is too low for separation in the electric field.