Separation in these devices known as winnowing machines
[3], is achieved due to the difference between trajectories
of coarse and fine particles in the separation zone
(Fig. 1b). Their operation and efficiency are strongly affected
by the stochastic factors of the process, in particular
by uncertainties in feeding and particles’ aerodynamic interactions.
In most cases coarse particles prevent proper classification
of fines. Separation efficiency of these devices is
usually low. They are normally used for separation of solid
particles according to densities (e.g. grain from peel), rather
than by size. Sometimes crossflow separation in horizontal
streams is used in combination with other separation principles.