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The influence of vibration number Γ, amplitude A, and frequency of vibration f on the fluid dynamic behavior of a vibrofluidized bed operating with inert particles in the transient period of water evaporation and drying of different solutions was evaluated. The solutions investigated were sewage sludge, skimmed milk, and calcium carbonate of three different solids contents. The impact of feed rate and vibration parameters on the dynamic behavior of variables such as pressure drop and inlet air velocity was determined. Based on the results it was verified that the operation at A = 0.015 m improved the bed dynamics and the gas-particle contact in the wetted beds. As different dynamic behaviors may be obtained under the same Γ value, the values of A or f must be informed together with Γ for a complete characterization of vibration effects. [ABSTRACT FROM AUTHOR]

The fluid dynamic behavior of a vibrofluidized bed operating with Geldart C particles was studied. The experiments were conducted in order to observe the influence of amplitude, frequency, and dimensionless vibration number on the minimum fluidization velocity, pressure drop, and standard deviation obtained. It was noted that the dimensionless vibration number should be used very carefully if it is to be the unique parameter to set the vibrational effect of the bed fluid dynamics. The results clearly indicate that the fluid dynamic behavior of the bed is very dependent on the different combinations of amplitude and frequency for the same dimensionless vibration number. Therefore, the use of the amplitude or frequency of vibration and the dimensionless vibration number is recommended for a better characterization of the vibrational effects on the fluid dynamic behavior of the particle bed. [ABSTRACT FROM AUTHOR]

The purpose of this work is to evaluate the operation of a vibrofluidized bed of inert particles in the transient and steady-state regimes for water evaporation and for drying of domestic sewage sludge. The feeding rate was initially set on 10 mL/min and this value has been gradually raised at 4 mL/min increments until saturated moist conditions were obtained at the bed exit. The bed was operated at 80 and 100°C, with inlet air velocities 20 and 40% above the minimum fluidization velocity. The dimensionless vibration numbers (Γ) were 0.00 and 4.00, the latter one with amplitudes of 0.003 and 0.015 m. For the conditions investigated, the effect of Γ on the drying dynamics was observed to depend on the amplitude and frequency of vibration. The use of vibration with lower amplitude and higher frequency provided the highest powder production. For paste feeding rates from 14 to 38 mL/min, the moisture content of the dried sewage sludge powder varied from around 5 to 10% on a wet basis, tending to increase with the increase of paste feeding rates. [ABSTRACT FROM AUTHOR]

The aim of this work is analyzing experimentally the fluid dynamic, thermal, and mass transfer behavior during the transient period of paste drying process in spouted beds. The pasty materials used in this study were water, sewage sludge, skimmed milk, and calcium carbonate. Glass beads of 2.18 mm diameter and 2512.70 kg/m3 density were used as inert particle. Drying experiments were conducted with spouted beds under two different inlet air velocities, 15 and 30% higher than the minimum spouting velocity, and two ranges of temperature, 80 and 100°C. From these experiments, values of the bed pressure drop, spouting air velocity, particle bed temperature, exhaustion air temperature, and the humidity profile of gas and liquid phases during the transient period were obtained. The results indicate that the analysis of the transient drying period is an adequate and encouraging technique to obtain further information in order to understand the paste drying process in spouted beds. [ABSTRACT FROM AUTHOR]

A numerical study was carried out on the parametric sensitivity of the fluid dynamic variables for a draft tube spouted bed (SB) with bottom particles feed. The sensitivities of variables such as the air and particle velocities and voidages in the spout region, as functions of key model parameters, like the spout–annulus air distribution, solids recirculation rates and gas–particle drag coefficient were determined. The model was numerically integrated and sensitivities obtained by the central differences approach. The sensitivities were seen to depend on air inlet flowrates and heights in the bed. For air flowrates close to the minimum spouting velocity the model is very sensitive to all the parameters studied. In most cases, the variables were moderately to highly sensitive to air distribution in the bed. On the other hand, the variables were minimally to moderately sensitive to the drag coefficient and solids recirculation rates. The maps of sensitivity obtained provide useful information for planning of the probe location, hydrodynamic modeling and directing of future work on SB with bottom particles feed. [ABSTRACT FROM AUTHOR]