Material processing apparatus (20) includes a housing (22) with a plurality of vertically stacked inverting pan conveyors (42, 44) therein. Each conveyor (42, 44) includes a plurality of conveyor pans (50) traveling between and around aligned front and rear sprocket pairs (90, 92) to define upper and lower conveyor runs (52, 54). Each pan (50) has a perforated base plate (56) presenting a pair of opposed material-supporting surfaces (58, 60). As the pans (50) traverse the sprocket pairs (90, 92), they are inverted, and material (110) carried by the upper run pans (50) is transferred to the lower run pans (50) by passage of the material around and/or between the sprocket pair (90).