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.