Rotary Drum Dryer Method
The mostly used process for drying brewer’s spent grain is performed by means of rotary ovens requiring a high initial investment. Drying by rotary ovens does not alter the final product features as long as the process is not performed under high temperatures during prolonged periods. To prolong the storage time of spent grains and to reduce their mass (consequently to lower the transportation cost), spent grains need to be dried to about 10% moisture content.
The traditional drying operation (heated-air drying in rotary-drum dryers) is energy-intensive. To save energy, superheated steam (SS) could be used for drying spent grains.
The circulation of SS in the closed-loop drying system can reduce the energy wastage that occurs with hot-air drying. Also, the exhaust steam produced from the evaporation of moisture from the wet product can be used in other operations in the distilleries, such as cooking raw materials, stripping and rectifying distillation of ethanol, and concentrating residual stillage. In addition to the reduced energy consumption, drying in SS has numerous other merits compared with traditional hot-air drying.
These are: a reduction in the environmental impact, an improvement in drying efficiency, the elimination of fire or explosion risk, and a recovery of valuable volatile organic compounds.
However, the application of...