Rotary drum dryers are widely used in industrial agriculture because they can process large volumes of green crops in a short time, but the high temperatures required for rapid evaporation often cause thermal degradation, reducing essential nutrients, while intense moisture transfer can make the material brittle, leading to physical damage and quality loss. Since many dryers are designed for multiple materials, they are rarely optimized for the specific thermal properties and drying kinetics of a single crop, resulting in significant energy waste as excess fuel is used to reach the desired moisture level.These issues are particularly evident when drying high-moisture corn silage, a fermented mixture of greens and immature kernels. This doctoral thesis establishes a benchmark for optimal operation of an industrial rotary dryer using production data collected from equipment in Olds, Alberta, which was used to calibrate a mathematical model for dryer optimization. Four system configurations were analyzed: a single dryer (baseline), a single dryer with exhaust air recirculation directly and via a heat exchanger, two dryers in series at reduced temperatures, and two dryers in series with exhaust air recirculation. In the base case, drying from 65% moisture (w.b.) at a feed rate of 3.5 t/h required 4,400 kJ/kg of water, with conditions adjusted to achieve 10% exit moisture, while the long-term average energy use of the production dryer was 6,360 kJ/kg of evaporated moisture. Modeling results showed that exhaust air recirculation up to 60% significantly reduced energy consumption, whereas higher rates decreased drying efficiency due to moisture buildup, and two-stage drying lowered operating temperatures while reducing overall specific energy use. Across a temperature range of 50–200°C, no clear relationship was observed between drying temperature and nutritional properties, although biomass breakage exceeded 20% when moisture content dropped to 5%.By integrating experimental results, full-scale production data, and validated modeling, this study identifies practical strategies to improve energy efficiency while maintaining corn silage quality.
Mohammad Aliahmadi (Thu,) studied this question.