These devices, known as Zigzag classifiers [4], are cascades
of several inclined branch pipes of a rectangular cross
section arranged to form a vertical zigzag channel (Fig. 2a).
Air flowing from below scavenges the particles fed from
above in cross-current direction. The flow field within the
chamber has vortexes in the turn points, where the fines are
dragged by the stream, and the coarse particles cross it towards
the opposite wall and pour down. Separation occurs in
a cross-flow process. Sequential pipes’ arrangement enables
multiple scavenging to improve the separation efficiency.
Several types of Zigzag classifier are produced by Alpine
[5] for separation of ferruginous ore, fertilizers, plastic,
wooden dust, etc. at cut sizes ranging from 0.1 to 10 mm.
The number of parallel chambers varies from one to 16
with output ranging from 1 to 10 t/h.