Process of separating solid granular metallurgical products and their precursors and apparatus

Claim 1

In a process of separating solid granular metallurgical products and their precursors by providing a plurality of linearly vibrating inclined screens spatially arranged one over the other, in a housing, each screen having an inclination greater than that of the screen above and wherein the width of the mesh openings in each screen is less than that of the screen above and the width of the mesh openings of each screen is 1.5 to 15 times larger than the desired parting size, and feeding the solids to be separated onto the uppermost screen at the upper end of said housing, the coarser solids being deflected in the direction of inclination of said uppermost screen, the finer solids initially falling through freely and onto lower screens having smaller mesh openings being deflected also in the direction of inclination of said lower screens, the coarsest solids fraction being withdrawn as overflow from said uppermost screen, finer solids fractions being withdrawn as overflow from following screens, and solids which have passed through all screens being withdrawn as a finest fraction, the improvement which comprises flowing a gaseous fluid through at least part of the working space required for screening in a direction approximately transverse to the direction in which said solids pass through said screens at a rate and in an amount to effect entrainment of those solids having a lower specific gravity between successive adjacent screens by said gaseous fluid flowing through said working space and to effect the resulting gaseous fluid laden with said solids of lower specific gravity to flow into a separating chamber, and separating at least the coarser of said solids of lower specific gravity from the flowing gaseous fluid in said separating chamber, wherein said separating step includes providing a separating plate in the separating chamber which is rearwardly and upwardly inclined and has a forward edge extendible generally parallel to the level of each of said screens, separating said coarser solids on said plate by sliding same down on said plate and withdrawing same through a discharge opening from the lower portions of said separating chamber, and withdrawing said gaseous fluid and the finer solids entrained thereby upwardly behind said plate through the upper portions of said separating chamber.