Effect of Gas Density on the Hydrodynamics of Bubble Columns and Three‐Phase Fluidized Beds

Macchi, Arturo; Bi, Hsiaotao T.; Grace, John R.; McKnight, Craig A.; Hackman, Larry P.

doi:10.1002/cjce.5450810368

Cited by 12 publications

(16 citation statements)

References 25 publications

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“…Similarly, for the heterogeneous regime, G varies from 0.221 to 0.295. At such high gas velocities, only the data set of Macchi et al 30 was applicable, which is shown in increasing order with three different gases employed by them. Parity plots capturing the effects of all above-mentioned parameters are shown in Figure 7B,C for V G ) 0.045 m/s and V G ) 0.145 m/s, respectively, for the SVRbased model.…”

Section: Parametric Sensitivity Analysismentioning

confidence: 99%

Development of Correlations for Overall Gas Hold-up, Volumetric Mass Transfer Coefficient, and Effective Interfacial Area in Bubble Column Reactors Using Hybrid Genetic Algorithm-Support Vector Regression Technique: Viscous Newtonian and Non-Newtonian Liquids

Gupta

Merchant

Bhat

et al. 2009

Ind. Eng. Chem. Res.

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The objective of this study was to develop hybrid genetic algorithm-support vector regression (GA-SVR)-based correlations for overall gas hold-up ( G ), volumetric mass-transfer coefficient (k L a), and effective interfacial area (a) in bubble column reactors for gas-liquid systems employing viscous Newtonian and non-Newtonian systems as the liquid phase. The hybrid GA-SVR is a novel technique based on the feature generation approach using genetic algorithm (GA). In the present study, GA has been used for nonlinear rescaling of attributes. These, exponentially scaled, are eventually subjected to SVR training. The technique is an extension of conventional SVR technique, showing relatively enhanced results. For this purpose an extensive literature search was done. From the published literature, 1629 data points for viscous Newtonian and 845 data points for viscous non-Newtonian systems for G , 500 data points for viscous Newtonian and 556 data points for viscous non-Newtonian systems for k L a, and 208 data points for viscous non-Newtonian systems for a, respectively, were collected. These data sets were collected spanning the years 1965-2007. Correlations were developed after taking into account all the parameters affecting G , k L a, and a such as column and sparger geometry, gas-liquid properties, operating temperature, pressure, and superficial gas and liquid velocities. The correlations thus developed gave prediction accuracies of 0.994 and 0.999 and average absolute relative errors (AARE) of 3.75 and 1.65% for viscous Newtonian and non-Newtonian systems for G , prediction accuracies of 0.983 and 0.998 and AARE of 8.62 and 1.91% for viscous Newtonian and non-Newtonian systems for k L a, and prediction accuracy of 0.999 and AARE of 1% for viscous non-Newtonian systems for a, respectively. These correlations also showed much improved results when compared with all the existing correlations proposed in literature. To facilitate their usage, all the hybrid GA-SVR-based correlations have been uploaded on the web link http://www.esnips.com/web/UICT-NCL.

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Section: Parametric Sensitivity Analysismentioning

confidence: 99%

Development of Correlations for Overall Gas Hold-up, Volumetric Mass Transfer Coefficient, and Effective Interfacial Area in Bubble Column Reactors Using Hybrid Genetic Algorithm-Support Vector Regression Technique: Viscous Newtonian and Non-Newtonian Liquids

Gupta

Merchant

Bhat

et al. 2009

Ind. Eng. Chem. Res.

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“…More recently, Macchi et al (2003) studied the effect of gas density on the hydrodynamics of coarseparticle, three-phase fluidized beds. The solid phase was represented by borosilicate glass beads, while a 55 wt% aqueous glycerol solution formed the liquid phase.…”

Section: Bubble Breakupmentioning

confidence: 99%

Results of Large-Scale Testing on Effects of Anti-Foam Agent on Gas Retention and Release

Stewart¹,

Guzman-Leong²,

Arm³

et al. 2008

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Testing SummaryThe U.S. Department of Energy (DOE) Office of River Protection's Waste Treatment and Immobilization Plant (WTP) will process and treat radioactive waste stored in tanks at the Hanford Site. The waste treatment process in the pretreatment facility will mix both Newtonian and non-Newtonian slurries in large process tanks. Process vessels mixing non-Newtonian slurries will use pulse jet mixers (PJMs), air sparging, and recirculation pumps. An anti-foam agent (AFA) will be added to the process streams to prevent surface foaming but may also increase gas holdup and retention within the slurry.Some gas retention tests that were carried out in nonprototypic systems-bubble columns and impeller-mixed vessels-indicated trends that posed process and flammable-gas concerns . Both types of nonprototypic results indicated that the presence of AFA in a chemical simulant of Hanford Tank 241-AZ-101 high-level waste (HLW) might increase gas retention by a factor of 10 or more over that in clay without AFA, the simulant on which WTP design studies were based (see Section 1.2). In addition, the increase over clay holdup was greater at lower simulant yield stress, implying that the 30-Pa simulant results, which had been used for WTP design, might not bound gas retention.The work described in this report addresses gas retention and release in simulants with AFA through prototypic testing and analytical studies. This test program was established to determine whether the AFA has as strong an effect in a large-scale prototypic mixing system as it did in the small-scale nonprototypic tests. Gas holdup and release tests were conducted in a 1/4-scale replica of the lag storage vessel operated in the Pacific Northwest National Laboratory (PNNL) Applied Process Engineering Laboratory using a kaolin/bentonite clay and an AZ-101 chemical simulant with non-Newtonian rheological properties representative of actual waste slurries. Additional tests were performed in a smallscale mixing vessel in the PNNL Physical Sciences Building using liquids and slurries representing major components of typical WTP waste streams to address the fact that simulants delivered to the WTP will come from other tanks in addition to 241-AZ-101. Analytical studies were directed at discovering how the effect of AFA might depend on gas composition, and a model was developed for predicting the effect of AFA on gas retention and release in the WTP, including the effects of mass transfer to the sparge air.The prototypic gas retention and release tests performed in this test program indicate that gas holdup with AZ-101 simulant with AFA is higher than it is in clay, but not to the extent that initially raised WTP design concerns. In addition, the trend to a higher increase in holdup with decreasing simulant yield stress was not seen in the prototypic system. The work at PNNL was part of a larger program that included tests conducted at Savannah River National Laboratory (SRNL) that is being reported separately. SRNL conducted gas holdup tests in a small-scale m...

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“…Bubble column reactors are operated under high pressure in a variety of chemical processes, such as hydrocracking of petroleum residue (5–21 MPa), Fischer‐Tropsch synthesis (1–5 MPa), benzene hydrogenation (5 MPa), and oxidation of para‐xylene to terephthalic acid (0.3–3 MPa) . In the last three decades, many researchers have found that pressure has a significant effect on the hydrodynamics of bubble columns.…”

Section: Introductionmentioning

confidence: 99%

A unified theoretical model for breakup of bubbles and droplets in turbulent flows

et al. 2014

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Pressure has a significant effect on bubble breakup, and bubbles and droplets have very different breakup behaviors. This work aimed to propose a unified breakup model for both bubbles and droplets including the effect of pressure. A mechanism analysis was made on the internal flow through the bubble/droplet neck in the breakup process, and a mathematical model was obtained based on the Young–Laplace and Bernoulli equations. The internal flow behavior strongly depended on the pressure or gas density, and based on this mechanism, a unified breakup model was proposed for both bubbles and droplets. For the first time, this unified breakup model gave good predictions of both the effect of pressure or gas density on the bubble breakup rate and the different daughter size distributions of bubbles and droplets. The effect of the mother bubble/droplet diameter, turbulent energy dissipation rate and surface tension on the breakup rate, and daughter bubble/droplet size distribution was discussed. This bubble breakup model can be further used in a population balance model (PBM) to study the effect of pressure on the bubble size distribution and in a computational fluid dynamics‐population balance model (CFD‐PBM) coupled model to study the hydrodynamic behaviors of a bubble column at elevated pressures. © 2014 American Institute of Chemical Engineers AIChE J, 61: 1391–1403, 2015

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Effect of Gas Density on the Hydrodynamics of Bubble Columns and Three‐Phase Fluidized Beds

Cited by 12 publications

References 25 publications

Development of Correlations for Overall Gas Hold-up, Volumetric Mass Transfer Coefficient, and Effective Interfacial Area in Bubble Column Reactors Using Hybrid Genetic Algorithm-Support Vector Regression Technique: Viscous Newtonian and Non-Newtonian Liquids

Development of Correlations for Overall Gas Hold-up, Volumetric Mass Transfer Coefficient, and Effective Interfacial Area in Bubble Column Reactors Using Hybrid Genetic Algorithm-Support Vector Regression Technique: Viscous Newtonian and Non-Newtonian Liquids

Results of Large-Scale Testing on Effects of Anti-Foam Agent on Gas Retention and Release

A unified theoretical model for breakup of bubbles and droplets in turbulent flows

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