The effect of column diameter and bed height on minimum fluidization velocity

Rao, Akhil; Curtis, Jennifer; Hancock, Bruno C.; Wassgren, Carl

doi:10.1002/aic.12161

Cited by 71 publications

(28 citation statements)

References 15 publications

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“…In addition, it is noted that for 104 μm solid particles ( D h / d p = 96.15), U mf,e is slightly higher than U mf,t , which indicates that the friction stress still exits and influences U mf even for higher D h / d p (96.15). Rao et al also found that the wall effect affected the fluidization characteristic when D h / d p was up to 150 in a 16 mm bed.…”

Section: Resultsmentioning

confidence: 95%

“…In macroscale three‐phase fluidized beds, the static bed height scarcely affects U Lmf , which can be seen from many formulas for predicting U Lmf . However, the static bed height exerts a greater influence on the minimum fluidization velocity for the liquid‐solid or gas ‐solid systems at a smaller bed diameter . Figure shows the effect of the static bed height on U Lmf for gas‐liquid‐solid MFB with bed diameter of 10 mm of 740 μm solid particles.…”

Section: Resultsmentioning

confidence: 99%

“…They proposed a new empirical equation containing particle diameter and bed height. Rao et al implemented U mf experiments in 16 and 24 mm gas‐solid fluidized beds, and proposed a new, semicorrelated model including Janssen's wall effect . The modified Ergun's equation incorporated the influence of bed diameter and static bed height so that it could reasonably predict U mf over a range of the solid particle size, bed height, and bed diameter.…”

Section: Introductionmentioning

confidence: 99%

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Minimum fluidization velocity in gas‐liquid‐solid minifluidized beds

Liu

2016

AIChE Journal

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The initial fluidization characteristics of gas-liquid-solid minifluidized beds (MFBs) were experimentally investigated based on the analyses of bed pressure drop and visual observations. The results show that U Lmf in 3-5 mm MFBs can not be determined due to the extensive pressure drop fluctuations resulting from complex bubble behavior. For 8-10 mm MFBs, U Lmf can be confirmed from both datum analyses of pressure drop and Hurst exponent at low superficial gas velocity. But at high superficial gas velocity, U Lmf was not obtained because the turning point at which the flow regime changes from the packed bed to the fluidized bed disappeared, and the bed was in a half fluidization state. Complex bubble growth behavior resulting from the effect of properties of gas-liquid mixture and bed walls plays an important role in the fluidization of solid particles and leads to the reduction of U Lmf . An empirical correlation was suggested to predict U Lmf in MFBs.

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Section: Resultsmentioning

confidence: 95%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Minimum fluidization velocity in gas‐liquid‐solid minifluidized beds

Liu

2016

AIChE Journal

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“…Figure illustrates the effect of H 0 on U MF , and it shows that the U MF decreases with an increase in the H 0 . On one hand, the U MF increases as the H 0 is increased, which is due to the larger resistance of wall in the DTSFB, making it more difficult to fluidize the particles . On the other hand, the resistance of the annular region increases with the increase in H 0 , which prevents the spouting gas bypass in the annular region, resulting in a decrease in U MF .…”

Section: Resultsmentioning

confidence: 99%

“…Generally, minimum fluidizing velocity has been studied in a fluidized bed as an important parameter . Some of the literature proposed correlations for predicting the minimum fluidizing velocity in fluidized beds, and Moradi et al studied the effect of the geometry of a spouted bed on the minimum fluidization velocity numerically, which was calculated based on the volume fraction distribution comparison.…”

Section: Introductionmentioning

confidence: 99%

Effect of bed geometry on operating pressure drop and minimum fluidizing velocity in a draft tube spout‐fluid bed

Zhang

Huang

et al. 2019

Can J Chem Eng

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Operating pressure drop and minimum fluidizing velocity were studied in a flat spout-fluid bed using sub-millimetre grade silicon particles. The influence of introducing a nonporous draft tube of different configurations as well as fluidizing gas on the two parameters was investigated. A comparison of fluidizing gas systems indicated that introduced gas restrained gas bypassing to lower the minimum fluidizing velocity; however, the operating pressure drop was higher than systems without the existence of fluidizing gas. Two new correlations that took into account the effects of bed geometry and fluidizing gas on the operating pressure drop and minimum fluidizing velocity were developed based on the experimental data, which were in agreement with the present experiments.

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Classifying the fluidization and segregation behavior of binary mixtures using particle size and density ratios

et al. 2011

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Experimental investigations show that fluidized binary mixtures exhibit varied pressure drop profiles and segregation patterns, depending on the level of disparity due to size and/or density differences. In this study, different mixture types are mapped on a graph of density versus size ratios. It is found that the ratio of the minimum fluidization velocities of individual components can be used to categorize these mixtures. A simple correlation is developed to compute the ratio of the minimum fluidization velocities based on the density and size ratios. Categorizing the binary mixtures in this manner gives a qualitative understanding of how the different mixtures behave on fluidization. V V C 2010 American Institute of Chemical Engineers AIChE J, 57: 1446AIChE J, 57: -1458AIChE J, 57: , 2011 Keywords: fluidization, segregation, mixing, binary mixture IntroductionFluidized beds are popular in industry. For example, drying of pharmaceutical powders 1 and catalytic cracking of petroleum and coal combustion for generating electricity 2 are commonly performed in fluidized beds. Fluidization operations are based on contact between a fluid stream and a mixture of solid materials, which varies for each process. A common observable phenomenon associated with multisolid beds is that they may segregate when subjected to fluidization. Segregation is primarily due to particle size and/or density differences.The segregation tendency of a powder mixture influences the overall process efficiency and, hence, segregation via fluidization is one of the key areas of fluidization research. Much experimental data exists in the literature concerning fluidized bed segregation, yet the current understanding of the mechanisms controlling multisolid fluidization segregation is very poor, even for two-component particle mixtures. In fact, for a simple binary mixture fluidized by a gas, there are a variety of pressure drop profiles that have been observed, and the different pressure drop profiles lead to different segregation patterns. For example, Formisani et al. 3 presented several binary mixtures having large density and/ or size ratios that fluidize at two different velocity points, while Joseph et al. 4 has reported mixtures that fluidize at a single velocity point, just like a monocomponent powder. Marzocchella et al.5 studied an extremely disparate mixture that mixes well at low velocities, just beyond the point of fluidization, but segregates at larger velocities. Complicating matters further, the phenomenon of layer inversion has also been observed in fluidized mixtures containing smaller, denser particles and coarser, less dense particles. 6This study is the first attempt to catagorize the various gas fluidized binary mixture types reported by various authors. In addition, a corelation between the minimum fluidization Correspondence concerning this article should be addressed to A. Rao at akhilrao@hotmail.com. is proposed that can be used to distinguish between these mixture types, the observed pressure drop profiles, and segr...

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The effect of column diameter and bed height on minimum fluidization velocity

Cited by 71 publications

References 15 publications

Minimum fluidization velocity in gas‐liquid‐solid minifluidized beds

Minimum fluidization velocity in gas‐liquid‐solid minifluidized beds

Effect of bed geometry on operating pressure drop and minimum fluidizing velocity in a draft tube spout‐fluid bed

Classifying the fluidization and segregation behavior of binary mixtures using particle size and density ratios

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