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The relationship between the peak pressure drops of the binary mixtures to the minimum spouting velocity was discussed. The trend of variation of pressure drop versus superficial gas velocities for binary particle mixtures in the spouted beds was found to be similar with that for the single sized particle system. At the same air velocity for jetsam and flotsam rich systems , the maximum pressure drop in the jetsam rich system was larger than the flotsam one.

The measured values of minimum spouting velocity were compared with some empirical correlations for single sized particles in spouted beds. Fluid Sci.

Spouted Bed and Jet Impingement Fluidization in Food Industry

The dynamic behavior of the model is dominated by the entrainment zone, which includes the effects of 3 key processes: 1 Granular particle flow from the annulus into the area immediately above the gas inlet; 2 Radial leakage of gas outward from the inlet zone in response to the inward flowing particles and; 3 Upward flow of the main part of the inlet gas and subsequent particle entrainment in response to the gas-particle drag. Recommendations are made for further improvements to the model.

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Committee Members C. A gradual buret is employed to add a known volume of glycerol to the bed, which is already in stable spouting regime. The addition of liquid under this condition assures a good homogeneity for liquid distribution on inert particles. For each given experimental condition, a measuring tape in millimeters fixed to the column wall is used to measure bed height. Thus, at a given glycerol concentration, the overall bed porosity, e a , in the annular region is determined. Q airflow rate curve is determined by decreasing Q for both dry and wet spouted beds.

The procedure used to determine the six adjustable parameters, a 1 , a 2 , b 1 , b 2 and c 1 , c 2 , is the one proposed by Trindade et al. As suggested by these authors, the heuristic particle swarm optimization method, developed by Kennedy and Eberhart , is chosen to optimize f obj , as it is robust and efficient enough to guarantee that the adjustable parameter values obtained are those representative of the global minimum of the objective function.

Table 4 shows the optimum values for the six parameters of the corrective functions in Equation 2. Based on these corrective functions of this work, the spouted bed operational variables, Q mj , D P mj , r mj , U a and P j , can be simulated. Based on the statistical analysis, the correlation coefficient r between these experimental and simulated data is 0.

Therefore, one can conclude that this model with the corrective functions in Table 4 can be used to estimate the other flow variables as a function of the amount of glycerol in the bed. These contribute to reduce the airflow rate crossing the spout-annulus interface and the particle motion in the annulus region.


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Thus, with the increase in glycerol concentration, a lower flow rate is needed to maintain the stable spouting regime as shown in Figure 4a. This prevents part of the inlet air from crossing the interface, causing a reduction in bed pressure drop, as shown in Figure 4b. Therefore, the simulated P j z curves, shown in Figure 5 , corroborate that the increase in glycerol concentration in the bed results in a decrease in gauge pressure at the spout-annulus interface. Figures 6a and 6b show the simulated profiles of the superficial air velocity in the annulus region, U a z , and of the spout radius, r mj z , as a function of glycerol concentration.

Such behavior can be explained due to the enlargement of the spout radius r mj , in spite of the decrease in airflow rate from spout to annulus region. Moreover, this is a characteristic shape for conical spouted beds in a specific range of values for parameter A 0. In spite of the fact that the U a z and r mj z profiles are only simulated, these are in agreement with experimental trends reported for the values for the magnitude of liquid binding forces on bridges in conical spouted beds, as shown by the theory of cohesive forces.

According to previous work see Bacelos et al. Thus, only at the base of the column, the radial air velocity component has enough radial inertial force components to break off the liquid bridges between inert particles and carry them along the spout until reaching the bed surface. This behavior not only maintains the stable spouting regime, but probably enlarges the spout at the column base, as shown in Figure 6b.

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"Scaleup and hydrodynamics study of gas-solid spouted beds" by Shreekanta Basavaraj Aradhya

By comparing this set of data to one reported for egg emulsion see Costa Jr. This implies an increase in U a at the column base and its reduction at the top see Figure 6a , favoring particle agglomeration on the bed surface when the suspension is fed in the column top alone, as verified by Spitzner Neto et al. On the other hand, data obtained here differ from those reported for eucalyptus black liquor see Costa Jr. As well, U a z becomes higher at top of the column than at the base. This indicates that particle agglomeration starts near the base of the column due to the reduction in U a z in this region, as pointed out by Trindade et al.

Simulation of a spouted bed reactor

From these comparisons, one can see that the data presented are consistent with those for egg emulsion, which are obtained using the same equipment and inert particles. Consequently, the same transitional bed failure mechanism 0. Based on these experimental data, one can note there is evidence showing that the behavior of conical spouted bed fluid dynamics changes significantly with mixture of particles, pastes or suspensions.

As has been reported in the literature, such changes can be predicted well taking into account the effect of cohesive forces on the fluid dynamics behavior of the conical spouted bed. Therefore, the previous model has been demonstrated to be effective in predicting spouted bed operational variables. As shown in the Discussion section model prediction plays an important role in processes of drying of pastes. It allows determination of spout shape and annular superficial velocity profiles as a function of the suspension added to the spouted bed of inert particles, and shows where in the bed particle agglomeration should start.

This permits researchers to better understand both fluid dynamics and drying phenomena in wet spouted beds. Moreover, by comparing the model verification with the same bed and with different suspensions, it can be noted that the type of bed failure mechanism dictates the spouting airflow behavior in the wet bed, whereas the paste characterizes the magnitude of change in the operational spouted bed variables. Aguado, R. Yields and Product Composition, Ind. Ayub, G. Bacelos, M. Drying Technol. Barret, N. Mujumdar, A. Birchal V. Birchal, V. Bilbao, J. Charbel, A.

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Cordeiro, D. Correa, N. Costa, I. Costa Jr. Spouted beds of inert particles for drying suspensions. Daleffe, R.


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