Although there are some models available in the literature for paste drying in spouted beds, few of them have focused on transient analysis of dynamical systems. Our objective was to integrate experiments and simulations of a dynamic model to investigate the transient response to disturbances and interruptions in the feed flow during paste drying in a spouted bed with inert particles. The spouted bed consisted of a cylindrical column with 50.0 cm of height and 20.0 cm of diameter. Drying tests were performed at inlet gas temperatures of 70 °C and 100 °C and inlet air flow 30% above the minimum spouting velocity. A 5% w/w suspension of calcium carbonate was used as paste material, and glass spheres of 2.2 mm were used as inert materials. Different patterns of step function changes were tested in the paste feed flow rate. A lumped parameter model was used to predict mass and heat transfer during the drying. Experiments and simulations were in good agreement.

The drying process of microcrystalline cellulose and adipic acid particles in a cylindrical fluidized bed was investigated using the Gaussian spectral technique to monitor fluid–dynamic regime transitions associated with surface moisture loss. Pressure fluctuation signals were recorded and analyzed to assess hydrodynamic behavior. Excess moisture significantly alters the bubbling characteristics of the bed, leading to instability in the fluidization regime. The results demonstrated that the Gaussian spectral technique effectively captured these hydrodynamic changes, particularly at the critical moisture content threshold, when compared with the drying rate curves of the materials. For microcrystalline cellulose and adipic acid particles, it is reasonable to conclude that a mean central frequency above 5.75–6.0 Hz and a standard deviation exceeding 3.7–3.8 Hz correspond to a bubbling regime, indicating that the critical drying point has been reached. This approach provides a non-intrusive and sensitive method for identifying transitions in the drying process, offering a valuable tool for real-time monitoring and control. The ability to track fluidization regime changes with high precision reinforces the potential of this technique for optimizing drying operations in the pharmaceutical, food, and chemical industries.

Apesar da literatura reportar vários modelos matemáticos empregados para a secagem de pasta em leito de jorro, poucos trabalhos propõem estudar o regime tran...