Mathematical description of pressure drop profile for the 1-valve and 2-valve bed collapse experiment

Cherntongchai, Parimanan; Innan, Thaksina; Brandani, Stefano

doi:10.1016/j.ces.2010.12.001

Cited by 10 publications

(7 citation statements)

References 31 publications

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“…This can be attributed to negative momentum acquired by solids during their fall under the gravity from heights attained during their fluidization. Another factor that can lead to this behavior is the sudden lacunae in the air supply to the test section due to the flow interruption that causes the air present in the upper section of the column to flow backwards [17]. On the other hand, global pressure transients are quite smooth.…”

Section: Resultsmentioning

confidence: 99%

Effect of Frequency on Pulsed Fluidized Beds of Ultrafine Powders

Ali

Al‐Ghurabi

Ajbar

et al. 2016

Journal of Nanomaterials

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Deagglomeration of ultrafine powders poses an important challenge towards their efficient and effective utilization. In the present study, we investigate the effect of frequency on the hydrodynamics of pulsed fluidized beds of ultrafine powders that show strong agglomeration behavior. We have carefully selected square waves of three different frequencies: 0.05 Hz, 0.10 Hz, and 0.25 Hz. The lowest frequency used here allowed the fluidized bed to settle completely before another pulse was introduced whilst the highest frequency ensured that the bed remained in a state of continuous turbulence between occurrences of consecutive pulses. On the other hand, the intermediate frequency pulse was just sufficient to complete the process of bed collapse before the start of the next pulse. Both local and global bed dynamics in all the three cases were rigorously monitored using fast response pressure transducers. The pressure transient data during the bed collapse were processed using the bed collapse model reported in the literature to compute the effective hydrodynamic diameter of agglomerates. Though there was substantial decrease in the agglomerate size, the effect of the frequency appeared to be rather insignificant as the global pressure transients remained rather insensitive to the change of the fluidization velocity.

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Section: Resultsmentioning

confidence: 99%

Effect of Frequency on Pulsed Fluidized Beds of Ultrafine Powders

Ali

Al‐Ghurabi

Ajbar

et al. 2016

Journal of Nanomaterials

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“…The efficacy of pulsed flow strongly depends on inlet flow and deaeration configurations. The effect of the deaeration strategy has been extensively studied in the context of bed collapse [ 42 , 43 , 44 ]. Once the inlet flow is stopped, the deaeration of the residual air critically affects the bed collapse process, which is clearly reflected in the evolution of pressure transient profiles in different regions of the bed [ 43 , 44 ].…”

Section: Introductionmentioning

confidence: 99%

Effect of Inlet Flow Strategies on the Dynamics of Pulsed Fluidized Bed of Nanopowder

et al. 2023

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The use of fluidization assistance can greatly enhance the fluidization hydrodynamics of powders that exhibit poor fluidization behavior. Compared to other assistance techniques, pulsed flow assistance is a promising technique for improving conventional fluidization because of its energy efficiency and ease of process implementation. However, the inlet flow configuration of pulsed flow can significantly affect the bed hydrodynamics. In this study, the conventional single drainage (SD) flow strategy was modified to purge the primary flow during the non-flow period of the pulse to eliminate pressure buildup in the inlet flow line while providing a second drainage path to the residual gas. The bed dynamics for both cases, namely, single drainage (SD) and modified double drainage (MDD), were carefully monitored by recording the overall and local pressure drop transients in different bed regions at two widely different pulsation frequencies of 0.05 and 0.25 Hz. The MDD strategy led to substantially faster bed dynamics and greater frictional pressure drop in lower bed regions with significantly mitigated segregation behavior. The spectral analysis of the local and global pressure transient data in the frequency domain revealed a pronounced difference between the two flow strategies. The application of the MDD inlet flow strategy eliminated the disturbances from the pulsed fluidized bed irrespective of the pulsation frequency.

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“…The residual air moves upward during a bed collapse in a conventional fluidized bed [22,28,29,31,33]. However, other deaeration strategies have also been suggested in the literature [24,26,34,35]. Santos et al [36] added a vent below the fluidized bed, which was active only during the collapse process, and termed this configuration as a double drainage arrangement.…”

Section: Introductionmentioning

confidence: 99%

“…Owing to the downward movement of the residual air, a negative pressure drop was prominently observed in the lower bed regions for the double drainage configuration. Cherntongchai, Innan [34] also used a modified air passage configuration and proposed a mathematical model for calculating the dense phase voidage and the solid velocity [35]. Lorences, Patience [26] used single drainage, double drainage, and zero drainage configurations to study the collapse dynamics of mixtures of VPO and FCC catalyst particles of different size distributions.…”

Section: Introductionmentioning

confidence: 99%

“…While the investigation of the collapse dynamics in the past mainly focused on the effect of the drainage configuration for the deaeration of the residual gas [24,26,34], the particle classification [17], and the fluidization assistance [27,29], there has not been any focused study on the effect of agglomeration induced size stratification along the bed height, which is a common occurrence in the case of the ultrafine nanoparticles. Any detailed investigation into this effect, however, requires a careful monitoring of the collapse dynamics in the different regions of the bed along its height to clearly delineate the effect of the size stratification of nano-agglomerates.…”

Section: Introductionmentioning

confidence: 99%

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Effect of Voidage on the Collapsing Bed Dynamics of Fine Particles: A Detailed Region-Wise Study

et al. 2022

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Bed collapse experiments provide vital information about fluidized bed hydrodynamics. In this study, the region-wise bed collapse dynamics of glass beads, titania (TiO2), and hydrophilic nanosilica (SiO2) particles with widely different voidages (ε) of 0.38, 0.80, and 0.98, respectively, were carefully investigated. These particles belonged to different Geldart groups and exhibited varied hysteresis phenomena and fluidization indices. The local collapse dynamics in the lower, lower-middle, upper-middle, and upper regions were carefully monitored in addition to the distributor pressure drop to obtain greater insight into the deaeration behavior of the bed. While the collapse dynamics of glass beads revealed high bed homogeneity, the upper middle region controlled the collapse process in the case of titania due to the size-based segregation along the bed height. The segregation behavior was very strong for nanosilica, with the slow settling fine agglomerates in the upper bed regions controlling its collapse dynamics. The collapse time of the upper region was 25 times slower than that of the lower region containing mainly large agglomerates. The spectral analysis confirmed the trend that was observed in the pressure transients. The clear presence of high frequency events at 20 and 40 Hz was observed in the nanosilica due to agglomerate movements. The residual air exiting the plenum was strongly affected by the bed voidage, being lowest for the nanosilica and highest for the glass beads.

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Mathematical description of pressure drop profile for the 1-valve and 2-valve bed collapse experiment

Cited by 10 publications

References 31 publications

Effect of Frequency on Pulsed Fluidized Beds of Ultrafine Powders

Effect of Frequency on Pulsed Fluidized Beds of Ultrafine Powders

Effect of Inlet Flow Strategies on the Dynamics of Pulsed Fluidized Bed of Nanopowder

Effect of Voidage on the Collapsing Bed Dynamics of Fine Particles: A Detailed Region-Wise Study

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