The design of gas sparged devices for viscous liquid systems

Bhavaraju, Sitaram; Russell, T. W. F.; Blanch, Harvey W.

doi:10.1002/aic.690240310

Cited by 202 publications

(90 citation statements)

References 11 publications

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“…In a bubble column filled with a power-law fluid, a solution of carboxymethylcellulose (CMC), no transition was observed in a range of superficial gas (Jin et al 2004, Lessard and Zieminski 1971, Prince and Blanch 1990. In a single-orifice bubble column, a significant amount of coalescence would be expected to occur within a height of roughly one columndiameter from the sparge tip (Bhavaraju et al 1978). Higuera (2004) conducted numerical analyses that described a string of bubbles being formed and coalescing near the nozzle in a highly viscous fluid.…”

Section: Appendix B -Qsls Data Analysis Methodologymentioning

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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Section: Appendix B -Qsls Data Analysis Methodologymentioning

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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“…Extensive research on gas-liquid contacting has been undertaken in conventional bubble columns and stirred tank vessels [1][2][3][4][5][6][7][8][9][10][11][12][13], and the latter has been the standard device in fermentation industries worldwide. The oscillatory baffled column (OBC) has recently emerged as a viable alternative to those vessels, since it can provide enhanced mass transfer performance [14,15].…”

Section: Introductionmentioning

confidence: 99%

Effect of hydrodynamics on mass transfer in a gas–liquid oscillatory baffled column

Oliveira

2004

Chemical Engineering Journal

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In this paper, we present an experimental study on mass transfer of oxygen into water in an oscillatory baffled column (OBC). The objective of this work is to establish the contribution of individual parameters, such as the size of bubbles and the gas holdup, to the overall volumetric mass transfer coefficient (k L a). Our results show that the gas holdup is the most important factor. The liquid-side mass transfer coefficient (k L ) is calculated directly from the experimental measurements of gas holdup, Sauter mean diameter and k L a, and an increase of k L with D 32 is observed. The results also show that, above a critical level of fluid oscillation, the mass transfer coefficients are mainly governed by the oscillatory operating conditions, while independent of the type of gas sparger.

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“…Bhavaraju et al (1978) developed an expression for the power input (q) to gas sparged vessels based on the expansion of bubbles as they ascend the column from pressure P2 to P I , a t volumetric gas flow rate Q:…”

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confidence: 99%

Bubble coalescence and break‐up in air‐sparged bubble columns

1990

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A phenomenological model is proposed for the rates of bubble coalescence and bubble break-up in turbulent gas-liquid dispersions. Bubble coalescence is modeled by considering bubble collisions due to turbulence, buoyancy, and laminar shear, and by analysis of the coalescence efficiency of collisions. Bubble break-up is analyzed in terms of bubble interactions with turbulent eddies. A method for the measurement of coalescence and break-up events in turbulent systems is described and used to test the validity of the proposed model. The measurement technique relies on the mixing of tracer gases within bubbles upon coalescence, in conjunction with Monte-Carlo simulations of coalescence events. Both distilled water and salt solutions are examined. Favorable agreement is found between the model and the individual coalescence and breakage rates, as well as with data obtained for the average bubble size and bubble size distribution. Michael J. Prince Harvey W. Blanch Department of Chemical EngineeringUniversity of California Berkeley, CA 94720Introduction Gas-liquid contactors find broad application as reactors and separation units in the chemical, mining, pharmaceutical and biochemical industries. In these systems the rate of transport of the gas to the liquid phase often limits productivity and is therefore a critical design criterion. Current design methods rely on empirical correlations which may not be confidently applied beyond the narrow range of operating conditions and geometries over which they were determined.The uncertainty in bubble column design arises from a lack of fundamental understanding of the hydrodynamics and rate processes which govern bubble size and thus interfacial area. Bubble size depends on a balance of coalescence and break-up rates in the vessel. No broadly applicable model for these rate processes in turbulent systems has yet been presented. This has been due to the inability to measure bubble coalescence and break-up in systems where high gas flow rates prevent direct visual observation.The objective of this study is to measure bubble coalescence and break-up rates in turbulent gas-liquid dispersions and to develop a model for these rate processes based on physicochemical and hydrodynamic principles. The ability of the model to adequately predict the individual experimental rate of coales- cence and break-up is used to judge its validity. In addition, the model is tested against its ability to'predict bubble size and bubble size distributions.The coalescence process is analyzed by examination of bubble collision events and the likelihood of collisions resulting in coalescence. Bubble break-up is examined in terms of bubble interactions with turbulent eddies. In addition to the theoretical development, an experimental method for the measurement of bubble coalescence and break-up rates in turbulent systems is described.The effect of inorganic electrolytes on coalescence and break-up rates is also examined. Much of the current interest in the prediction of bubble size stems from the desire t...

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The design of gas sparged devices for viscous liquid systems

Cited by 202 publications

References 11 publications

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

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

Effect of hydrodynamics on mass transfer in a gas–liquid oscillatory baffled column

Bubble coalescence and break‐up in air‐sparged bubble columns

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