Pellet cooling method and apparatus using alternate hot and cool air

Abstract

A pellet conditioning device (10) for the cooling and/or drying of preformed discrete pellets (148) is provided which includes an upright pellet-receiving bin (12) with a dual grate assembly (18) therein. The assembly (18) includes a stationary first grate comprising a plurality of upright, apertured grate wall members (86), and a shiftable second grate including a plurality of elongated, obliquely oriented plates (106) located between and in spanning relationship to adjacent pairs of the wall members (86). Shifting structure (20) is provided for selective and sequential translational, rectilinear shifting movement of the lower margins (110) of the plates (106) so as to successively open and close a pellet passageway (117) adjacent each lower margin (110). A duct and fan arrangement (38) is also provided with the bin (12) so as to draw cooling air currents through the grate assembly (18) and pellets (148) therein. The plates (106) may also be shifted upwardly to their maximum extent in order to dislodge pellet bridges above the grate assembly (18). In another embodiment a conditioning device (12a) includes alternately operable hot and cool air introduction assemblies (152, 154) disposed along the opposed ends of bin (12a). In operation, relatively hot air currents are delivered beneath the grate assembly (18) via assembly (152), whereupon the later is closed; the cool air inlet assembly (154) is then opened so as to cause introduction of ambient air into and through the bin (12a).