Abstract: Horizontal, negative pressure centrifugal separator apparatus (48, 248, 348, 448, 548) is provided for separating particulate material from an air stream that exhausts from the outlet of a horizontal, industrial size, rotary drum dryer (32). The centrifugal separator is especially adapted to be connected to the negative pressure inlet of a primary fan (42) which pulls large volumes of air through the rotary drum dryer. The separator apparatus includes wall structure which defines two aligned primary spiral separation plenum chambers (e.g. 78, 80) joined to an intermediate spiral discharge plenum chamber (e.g. 82), all of which intercommunicate. A pair of oppositely facing plenum chamber divider members each having a central aperture therein are mounted in the plenum chambers on opposite sides of the discharge plenum chamber and function as pressure regain stacks.

Abstract: A single pass, multiple stage, rotary drum heat exchange dryer (22) is provided for drying products such as distillers grains and includes a tubular shell (64) with a moist product inlet (66), an opposed dried product outlet (70), and an internal drying chamber (78). The chamber (78) includes a convection drying first stage (80), and conductive drying final curing stage (82) an intermediate stage (84); the stage (84) is subdivided into a plurality of preferably contiguous drying zones (86-92). The zones (86-92) include individual flighting assemblies (164, 214, 226, 234) which are of increasing density and present progressively increasing heat transfer ratios. Preferably, one of the initial zones has a heat transfer ratio of from about 1.5-2.5 ft−1, whereas another of the zones closer to the final stage has a heat transfer of from about 2.75-3.75 ft−1.