The product, whose flow rate can be adjusted, is evenly distributed over the entire sieve surface by means of a curtain. There are 24 sieve boxes. Thanks to the aspiration system, light materials with a wide gripping surface are suspended by negative air pressure, and they are separated from the semolina by going to the rear exit thanks to the movement of the purifier. The product, which is free from bran, is classified according to grain size by means of sieves.