The Relation Between Wetting Efficiency and Liquid Holdup in Packed Columns

Alicilar, Ahmet; Bi̇çer, Ahmet; Murathan, Atilla

doi:10.1080/00986449408936237

Cited by 28 publications

(23 citation statements)

References 27 publications

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“…Therefore, we concentrate on Froude number for liquid Fr L and varied it over a wide range including BF condition, because liquid hold-ups greatly depend on Fr L . 14) 3. Results and Discussion…”

Section: Initially Soaked Bedmentioning

confidence: 99%

Characteristics of Liquid Hold-ups in a Soaked and Unsoaked Fixed Bed

Kawabata¹,

Liu²,

Fujita³

et al. 2005

ISIJ Int.

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In most previous works, liquid hold-ups were studied by using a cold model of a fixed bed soaked prior to experiments. However, they did not consider that the dripping zone of a blast furnace is saturated with liquids or with evenly distributed droplets. In the present study, the characteristics of liquid hold-ups and liquid flow were investigated by using a one-dimensional cold model of a fixed bed soaked and unsoaked prior to experiments (initially soaked and unsoaked beds). Packed balls were five kinds, the diameters (D p ) of which ranged from 5.4 to 30 mm. Tap water was used as liquid. Contact angles (q) for these particle/liquid systems were about 70°and 10°for fluorine-coated particles and non-coated particles, respectively.Although, under bad wettability condition (q Լ 70°), total and static hold-ups for initially unsoaked bed packed with small balls are remarkably smaller than those for initially soaked bed, the difference in their hold-ups between initially unsoaked and soaked beds decreases with increasing ball size in the bed. In initially soaked bed, total and static hold-ups increase monotonically as ball size decreases, which means the specific surface area increases. On the other hand, in initially unsoaked bed, total and static hold-ups under bad wettability condition indicate maximum values at about D p ϭ10 mm and decrease abruptly in proportion to a decrease in particle size, despite an increase in the specific surface area. Only restricted liquid droplets and/or liquid rivulets are formed within the packed bed with good wettability condition (qԼ 10°) for initially unsoaked bed, nevertheless liquid is easy to spread out on the solid surface. The influence of the initial bed condition, soaked or unsoaked bed, on liquid hold-ups is great under bad wettability condition.KEY WORDS: ironmaking; blast furnace; dripping zone; fixed bed; liquid hold-ups; particle/liquid wettability; initially soaked and unsoaked beds.

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Section: Initially Soaked Bedmentioning

confidence: 99%

Characteristics of Liquid Hold-ups in a Soaked and Unsoaked Fixed Bed

Kawabata¹,

Liu²,

Fujita³

et al. 2005

ISIJ Int.

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“…In total, 973 liquid axial dispersion coefficient measurements have been collected from 22 published independent studies covering the period 1958–2001 4, 5, 8, 12–29. The database exhibits results on 14 packing material and shape combinations.…”

Section: Brief Overviewmentioning

confidence: 99%

“…Increasing the liquid dynamic viscosity causes a decrease in the liquid axial dispersion coefficient 15 Despite inclusion of a liquid holdup term in numerous correlations, the gas flow rate factor has been found to affect only marginally the liquid axial dispersion coefficient 4, 7, 8, 16, 22 The effects of the following variables remain uncertain however as no directed studies are available in the literature: column diameter, particle sphericity, surface tension, liquid density and gas density. …”

Section: Brief Overviewmentioning

confidence: 99%

Improving the prediction of liquid back‐mixing in trickle‐bed reactors using a neural network approach

Piché¹,

Larachi²,

Iliuta³

et al. 2002

J of Chemical Tech & Biotech

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Current correlations aimed at estimating the extent of liquid back-mixing, via an axial dispersion coef®cient, in trickle-bed reactors continue to draw doubts on their ability to conveniently represent this important macroscopic parameter. A comprehensive database containing 973 liquid axial dispersion coef®cient measurements (D AX ) for trickle-bed operation reported in 22 publications between 1958 and 2001 was thus used to assess the convenience of the few available correlations. It was shown that none of the literature correlations was ef®cient at providing satisfactory predictions of the liquid axial dispersion coef®cients. In response, arti®cial neural network modeling is proposed to improve the broadness and accuracy in predicting the D AX , whether the Piston±Dispersion (PD), Piston±Dispersion±Exchange (PDE) or PDE with intra-particle diffusion model is employed to extract the D AX . A combination of six dimensionless groups and a discrimination code input representing the residence-time distribution models are used to predict the Bodenstein number. The inputs are the liquid Reynolds, Galileo and Eo È tvos numbers, the gas Galileo number, a wall factor and a mixed Reynolds number involving the gas¯ow rate effect. The correlation yields an absolute average error (AARE) of 22% for the whole database with a standard deviation on the AARE of 24% and remains in accordance with parametric in¯uences reported in the literature.

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“…However, the yields are higher than those in the solution without packing. This result may be explained by the fact that the contact efficiency between the gas and liquid phases increases in the presence of packing [15]. Figure 3 shows the results of experiments where MnO 2 was used in addition to glass beads.…”

Section: Discussionmentioning

confidence: 99%

Catalytic air oxidation of manganese in synthetic waters

2005

Self Cite

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An attempt was made to study the oxidation of manganese by air in synthetic waters. A series of batch experiments were performed at different values of concentration, temperature and pH. Unoxidized manganese in the solution was determined by formaldoxime spectrometric method. Results of these studies indicated that the air oxidation of manganese soluble in water can be effectively performed in basic media and that oxidation yield increasedwith an increase in pH and concentration. The yield was very high in the presence of manganese dioxide, sepiolite or clinoptilolite in solution and, the oxidation was almost completed especially at high values of pH and concentration. The reaction was found to be first order with respect to Mn 2+ with a very low activation energy. A yield of 62 % was obtained for the air oxidation of wastewater taken from the treatment plant of Corum Municipality.

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The Relation Between Wetting Efficiency and Liquid Holdup in Packed Columns

Cited by 28 publications

References 27 publications

Characteristics of Liquid Hold-ups in a Soaked and Unsoaked Fixed Bed

Characteristics of Liquid Hold-ups in a Soaked and Unsoaked Fixed Bed

Improving the prediction of liquid back‐mixing in trickle‐bed reactors using a neural network approach

Catalytic air oxidation of manganese in synthetic waters

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