Apparatus of the type forced vortex air for classification of particulate material into a fine portion and a coarse portion, the apparatus comprising: a) a truncated cone shaped upper section (101) comprising a separating wheel (111) rotating about a substantially vertical axis, a vertically arranged inlet pipe (106) for supplying particulate material dispersed in an air flow, a conical feed distributor (107) having a tip end directed downwards and arranged concentrically with the inlet pipe (106) and the separating wheel, and a spiral shaped outlet (102) for removal of classified fine material dispersed in air, and b) a substantially truncated cone shaped lower section (103), the upper section of which exhibiting a secondary air inlet (105) arranged tangential to the circumference of the lower housing (103) to supply secondary air in a direction concurrently with the direction of rotation of the separating wheel (111) and a second outlet (104) for classified coarse particulate material.