Drying–toasting of presoaked soybean in fluidised bed. Modeling, validation and simulation of operational variants for reducing energy consumption

• A fluidised bed-model for drying–toasting of presoaked soybean at 100–160 °C was developed.
• The predicted bed moistures and temperatures were validated satisfactorily.
• The thermal efficiency increased from 9.1 to 39.3% at a bed height of 0.1 m usingair recirculation.
• The fluidised bed model is considered useful for product and equipment design.

Soybeans (Glycine max) contribute to healthy nutrition because of the high proportion and quality of proteins. In this work, a bed-level model was developed from kinetic studies carried out earlier, for simulating the drying–toasting of presoaked soybean in a fluidised bed at air temperatures between 100 and 160 °C. The predicted average bed moisture contents and temperatures were validated with purpose-measured experimental data. The air humidity decreased and temperature increased with time at the dryer outlet, approaching the inlet conditions. By using the validated model the thermal efficiency was calculated for bed heights between 0.1 and 0.3 m, considering a system where 90% of the exhaust air was recirculated. The efficiency increased from 9 to 39% at 0.1 m and from 24 to 63% at 0.3 m, indicating that the energy consumption can be substantially reduced. This model is considered useful both for product development and equipment design.