Drying of granular medium by hot air and microwaves. Modeling and prediction of internal gas pressure and binder distribution

• Comprehensive internal heat and mass transfer model validated with experimental data
• Liquid and gas filtration, surface liquid expulsion and binder advection included
• Simulations of processes with simultaneous application of hot air and micro-waves
• Speeding-up the process while maintaining low gas pressure and high binder content

With the aim of enhancing the industrial drying (hot air and microwaves) of inserts made of agglomerated sand and to assess product quality, a comprehensive internal heat and mass transfer model has been proposed. In this model, liquid and vapor transfer by filtration, liquid expulsion at the surface and binder transfer by advection were directly accounted for. This model was validated on the basis of the experimental average water and binder content and core temperature curves for drying trials at different operating conditions. Then, it was used for comparing the drying time, the internal pressure and the binder content calculated for several test processes. It was demonstrated that the simultaneous application of hot air and micro-waves provided a real possibility to dry faster and to maintain quite the same internal overpressure and overall binder content as for the reference (damage free) process. The heating power should be increased gradually during the process. The decrease of the drying time was around 30% with regard to the reference mild process.

Simulated internal gas phase pressure versus time for different drying conditions.Figure optionsDownload as PowerPoint slide