Hydrodynamic and mass transfer characteristics of sectionalized aerated slurry reactors

Zahradník, Jindřich; Drápal, Lubomír; Kaštánek, F.; Řezníčková, Jitka

doi:10.1016/0255-2701(92)87019-d

Cited by 13 publications

(6 citation statements)

References 19 publications

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“…[27] and Albal et al [28]. However, reduction of k L a with an increase of solid loading for a certain solid content range was referred by Sada et al [29] and Zahradnik et al [30], while Chandrasekaran and Sharma [31], Quicker et al [10] and Sada et al [11] presented increases in the k L a with the solid loading. Once again, these discrepancies may arise from differences in experimental conditions, such as physicochemical properties of the liquid and also, loading, size, density and wettability of solids.…”

Section: Air-water-hollow Glass Spheresmentioning

confidence: 93%

Effect of some solid properties on gas–liquid mass transfer in a bubble column

Mena

Ferreira

Teixeira

et al. 2011

Chemical Engineering and Processing: Process Intensification

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The knowledge about the effects of solids on gas-liquid systems and the respective physical mechanisms are not yet totally clarified. In this work, the effect of the solids on the mass transfer characteristics in a bubble column was studied experimentally for the systems air/water/expandable polystyrene (EPS) beads and air/water/glass beads. Volumetric liquid side mass transfer coefficient, k L a, was determined under different solid concentrations (up to 30 vol.%), superficial gas velocities (up to 2.7 mm/s) and mean diameters (1100, 770 and 591 m for EPS and 9.6 m for glass beads). The presence of EPS solids affects negatively k L a being this effect more pronounced for the smaller particles. Also, a decrease in k L a occurs when the solid loading increases. Experiments done with large polystyrene particles (d p ≥ 591 m) contaminated with very fine EPS particles (d p ∼ = 0.1 m) indicate that very fine particles play an important role on gas-liquid mass transfer. Mass transfer experiments in a hollow glass spheres three-phase slurry showed a dual effect of solids loading on k L a, contrarily to what happens with the previous particles. These results can be associated with the different surface properties of the particles studied. An empirical correlation for k L a on the experimental variables was developed.

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Section: Air-water-hollow Glass Spheresmentioning

confidence: 93%

Effect of some solid properties on gas–liquid mass transfer in a bubble column

Mena

Ferreira

Teixeira

et al. 2011

Chemical Engineering and Processing: Process Intensification

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show abstract

“…Further, it seems that the solid effect becomes independent from solid loading for higher gas velocities. Zahradnik et al (1992) studied the effect of some operating variables on hydrodynamics and mass transfer characteristics of multi-stage three-phase slurry reactors and found that the increasing concentration of solid particles (in the range 0-5 wt%) reduced the k L a values. Freitas and Teixeira (2001) working with a three-phase internal loop airlift reactor noticed a similar behavior for the effect of solids.…”

Section: Image Analysis Experimentsmentioning

confidence: 99%

“…For the smaller particles one notices a significant decrease of interfacial area at the higher solids loading. This may be due to an increase of bubble coalescence leading to a decrease in total superficial area (Zahradnik et al, 1992; u G x 10 3 (m/s) Fig. 9.…”

Section: Interfacial Area and Liquid Side Mass Transfer Coefficientmentioning

confidence: 99%

Using image analysis in the study of multiphase gas absorption

Mena

Pons

Teixeira

et al. 2005

Chemical Engineering Science

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For the air-water-calcium alginate beads system, the effect of the presence of solids on the mass transfer characteristics in a bubble column was experimentally studied. Volumetric liquid side mass transfer coefficient, k L a, specific interfacial area, a, and hence liquid side mass transfer coefficient, k L , were determined under different solid concentrations (0, 5, and 10 vol%), superficial gas velocities (up to 0.27 cm/s) and solid sizes (1.2 and 2.1 mm diameter). The bubble characteristics, namely the interfacial area, were obtained using an image analysis technique. This technique proved to be a suitable and practical method to characterize mass transfer phenomena in bubble columns for the range of operating conditions used. The solids affect negatively k L a, decreasing both a and k L , the effect being more pronounced for the smaller particles. For these particles the variation of k L a is due to the variation of its two components, while for larger particles k L a variation is due, essentially, to changes in k L as no significant differences in a were observed.

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“…The presence of solids has an impact on bubble properties and, by this way, on interfacial area. In some situations, solid particles induce bubble break-up, increasing a, in other cases the solids enhance bubble coalescence which results in bigger bubbles and consequently decreases g-l interfacial areas [5,[18][19][20]. This was attributed, in some studies, to an increase in the apparent slurry viscosity with increasing slurry concentration.…”

Section: Introductionmentioning

confidence: 99%

Temperature and solid properties effects on gas–liquid mass transfer

Ferreira¹,

Ferreira²,

Teixeira³

et al. 2010

Chemical Engineering Journal

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The knowledge about the effect of solid phase properties, at different temperatures, on gas-liquid transfer and the respective physical mechanisms has been poorly studied. In the present work, the temperature and solid properties (size and density) effects on the gas-liquid mass transfer characteristics in a bubble column were experimentally evaluated. Gas-liquid-solid systems formed by air/water/polyvinyl chloride (PVC) beads and air/water/expandable polystyrene (EPS) beads were used. For each system, volumetric liquid side mass transfer coefficient, k L a, was determined under different temperatures (20-35 • C), superficial gas velocities (up to 7.2 mm/s), solids sizes (210, 549 and 591 m) and concentration (up to 5 vol.%). The results show that the temperature plays an important role on mass transfer phenomena as k L a increases as temperature is increased. However, temperature does not have, significantly, influence on the solids effect on k L a. In what concerns the effect of the solids on k L a, a negative effect of their presence is observed being this effect more pronounced for the largest particles (for PVC). In addition, for the same solid size, a decrease in k L a occurs when the solid loading increases (observed in both cases, PVC and EPS). Complementary, bubble/particle interaction studies, using an image analysis technique, were also done aiming a better understanding of the effects of the two types of particles -PVC and EPS -on k L a values, being clearly confirmed that physical (e.g. density) and chemical properties of the solids are important parameters to be taken into account on mass transfer and hydrodynamic studies.Based on theoretical models for k L and a, an empirical correlation for k L a dependence on the experimental variables was developed. The experimental results were fitted with a mean deviation of 5%, that is similar to the experimental error (5%).

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Hydrodynamic and mass transfer characteristics of sectionalized aerated slurry reactors

Cited by 13 publications

References 19 publications

Effect of some solid properties on gas–liquid mass transfer in a bubble column

Effect of some solid properties on gas–liquid mass transfer in a bubble column

Using image analysis in the study of multiphase gas absorption

Temperature and solid properties effects on gas–liquid mass transfer

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