Patent ID: 7735658

Claim:
A classification apparatus for a powdery substance comprising a classification tube provided with an upper end opening, a closed lower end, a filter attached to the upper end opening, and at least two classification compartments divided by divider plates and lined up and down in the interior space thereof, each of the divider plates having at least one opening, the first classification compartment having a supply port for a powdery substance to be classified, a gas emission conduit extending from the outside into the first compartment through a peripheral wall, a distal end opening of the gas emission conduit being directed in a tangential direction of an inner peripheral surface at the vicinity of a bottom surface of the classification compartment, high pressure gas being supplied to the gas emission conduit from a gas supply source arranged outside the classification tube, a vortex flow being generated in the classification tube by the gas from the gas emission conduit and rising from the first classification compartment sequentially towards the higher classification compartments; and conveyance acceleration means for accelerating conveyance of the powdery substance by the vortex flow so as to prevent the powdery substance from remaining in the first classification compartment while the vortex flow is being generated, whereby the powdery substance of the first classification compartment is classified in every classification compartment according to the size while being conveyed by the vortex flow.