Abstract: A process for purifying crude silicon carbide lumps from an Acheson furnace comprising agitating the lumps in a drum having a cylindrical wall, its axis substantially horizontal and having openings of controlled size, smaller than said crude lumps, in said cylindrical wall, separating the particles passing through said controlled size openings according to size and recirculating oversize particles back to said rotating drum and finally recovering product retained in said drum.

Abstract: A cyclic screening apparatus (10) and method utilizes multiple air flows and differential air pressures to separate undersize and oversize particles from a mixture of 5 to 50 micron size particles. The apparatus (10) comprises a support (12) including a first conduit (14) connected to a blower (16). A lower undersize particle collecting housing (20) has a secondary air inlet (24) and outlet (26) connected to a suction fan (SF). A screen is clamped between the lower housing and an axially movable and pivotable upper receiving housing. An air distributor rotor (R) is slowly rotated below and directs the first air flow through the screen and into the upper chamber and through a lower portion (40) and against the bottom of lower housing. A rotary nozzle (80), with the help of incoming secondary air flow, disperses particulate material onto the screen below.