Analysis of continuous-flow grain dryers

The high-temperature continuous-flow dryer is the prevalent dryer type in the major grain-producing countries. The choice of a particular model is frequently based on the initial cost, rather than on technical factors such as energy efficiency and grain quality. This has led at times to the employment of low-quality dryers, and to the production of inferior-grade grain and the consumption of excessive fossil-fuel energy. This pa per shows that the dryer-manufacturing industry currently markets reasonably-priced, energy-efficient dryers which are able to produce excellent quality grain. Crossflow, mixed-flow, and concurrent-flow are at present the primary high-temperature dryer types. Simulation modelling is routinely used today in the industry for analysis and design, resulting in their improved grain-quality and energy-efficiency characteristics. The modern crossflow dryer is suitable for drying maize as feed; it is less expensive than mixed-Bow and concurrent-flow dryers. For the drying of rice (and food maize), mixed-flow and concurrent-flow dryers are recommended because of their superior grain-quality characteristics. Of these, the concurrent-flow models have, in general, the best energy efficiency. Several unconventional high-temperature dryers are occasionally used commercially for the drying of grains. included in this group are the steam, the rotary, and the fluidised-bed dryers. Although each of these dryer types has certain advantages, their high initial and operating costs have thus far prevented market penetration.