Optimization study of soybean intermittent drying in fixed-bed drying technology

Intermittent drying of materials is an alternative operation that aims at reducing energy consumption, improve the preservation of dried products or decrease effective drying time. Intermittent drying supplies the system with time-varying input air properties that are opposite to traditional operations, where air properties are constant at the dryer inlet. The major objective of this study is to establish the most satisfactory patterns of air temperature and velocity modulation at the dryer entrance to reduce energy consumption. This optimization study was based on a heterogeneous model for the drying of grains in fixed bed validated with experimental data. Intermittent and conventional operation experiments were conducted using equal energy consumption, and the influence of air temperature and velocity modulation on the drying rates related to the percentage of evaporated water were assessed. Results indicated that higher drying rates can be achieved under intermittent operation, and the validated model based on these results could reasonably predict temperature and moisture content profiles. Simulations pointed out that the best modulation patterns of air properties is a function of a variety of system conditions such as initial temperature and moisture content of both soybean and drying air. However, a tendency to reduce energy consumption was observed when the system operation is initially at high temperature and constantly at low velocity.