Pressure Effect on the Flow Fields and the Reynolds Stresses in a Bubble Column

Lee, D. J.; McLain, Brian K.; Cui, and Zhiwei; Fan, Liang‐Shih

doi:10.1021/ie000505y

Cited by 7 publications

(10 citation statements)

References 11 publications

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“…Therefore, the extent of liquid mixing is reduced at elevated pressures. Our recent study of flow fields and Reynolds stresses in high-pressure bubble columns using the laser Doppler velocimetry technique (Lee et al, 2001) also confirmed that the bubble-induced turbulence of the liquid phase is depressed as the pressure increases. The combined variations of liquid-phase turbulent fluctuations and internal liquid circulation give rise to the overall effect of pressure on liquid mixing.…”

Section: Effect Of System Pressuresupporting

confidence: 57%

Engineering Development of Slurry Bubble Column Reactor (Sbcr) Technology

Toseland¹

2002

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Project ObjectivesThe major technical objectives of this program are threefold: 1) to develop the design tools and a fundamental understanding of the fluid dynamics of a slurry bubble column reactor to maximize reactor productivity, 2) to develop the mathematical reactor design models and gain an understanding of the hydrodynamic fundamentals under industrially relevant process conditions, and 3) to develop an understanding of the hydrodynamics and their interaction with the chemistries occurring in the bubble column reactor. Successful completion of these objectives will permit more efficient usage of the reactor column and tighter design criteria, increase overall reactor efficiency, and ensure a design that leads to stable reactor behavior when scaling up to large diameter reactors. AbstractThis report summarizes the results of a Department of Energy-funded study on slurry bubble column reactors (SBCR). Alternate fuels projects need high reactor throughput for competitive economics so that reactors must operate in the churn-turbulent region of flow. Little data in this flow regime, especially at the conditions of high pressure and temperature for organic fluids found in an industrial reactor, existed at the inception of this project. This report summarizes the large body of fundamental data that was developed on these flows. It covers both the local liquid turbulence and large-scale liquid internal circulation aspects of flow in the SBCR. Where understood, the underlying mechanisms, which result in the macro-scale phenomena, are elucidated and modeled. Finally, new models for reactor design are also presented. Executive SummaryThe state of the art in design and modeling of bubble columns before the initiation of this project relied solely on the use of ideal flow patterns (e.g., perfectly mixed liquid and plug flow of gas) or on the use of the axial dispersion model (ADM). The use of ideal flow patterns can lead to serious over design, and the uncertainty in the values of the axial dispersion coefficients precludes a more accurate design based on the ADM. Since these models represent crude descriptions of the flow pattern in bubble columns and do not account for input from the fluid dynamics of the system, the scaleup of SCBR has been uncertain.The need for rapid scaleup and optimal commercialization for gas conversion processes necessitated an improved understanding and quantification of fluid dynamics and transport in slurry bubble column reactors. This report presents the results of an extensive experimental and theoretical program on SBCR.This program was conducted by a team comprising Air Products (APCI), Washington University in St. Louis (WU), The Ohio State University (OSU), Iowa State University (ISU) and Sandia National Laboratory (SNL). SNL participated as an active team member, but was supported by separate DOE funds; therefore, SNL's work will not be reported here.Bubble columns are complex. The complexity can be simplified in breaking up the phenomena occurring in bubble columns according to sc...

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Section: Effect Of System Pressuresupporting

confidence: 57%

Engineering Development of Slurry Bubble Column Reactor (Sbcr) Technology

Toseland¹

2002

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“…Reynolds normal and shear stresses at z/D ) 4 for the perforated plate sparger are shown in Figure 8. It can be seen that the normal stresses are much higher than the shear stresses as also observed by Lee et al 16 and Kulkarni et al 9 However, the axial-radial Reynolds shear stress (u′V′) is important to generate the liquid circulation in the column. 17,18 Hence, we have given the radial profiles for the same in Figure 9.…”

Section: K )mentioning

confidence: 69%

“…Reynolds normal and shear stresses at z / D = 4 for the perforated plate sparger are shown in Figure . It can be seen that the normal stresses are much higher than the shear stresses as also observed by Lee et al and Kulkarni et al However, the axial-radial Reynolds shear stress ( ) is important to generate the liquid circulation in the column. , Hence, we have given the radial profiles for the same in Figure . For the porous plate sparger, Reynolds shear stress is typically much small (except near the sparger), indicating that the circulation is not as strong as in case of perforated plate sparger.…”

Section: Resultsmentioning

confidence: 87%

Laser Doppler Anemometer Measurements in Bubble Column: Effect of Sparger

Bhole

Roy

Joshi

2006

Ind. Eng. Chem. Res.

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Measurements of flow pattern in a 150 mm i.d. bubble column were carried out using a laser doppler anemometer (LDA) in a forward scatter mode. A superficial gas velocity of 20 mm/s was used in all the experiments. Two different spargers (perforated plate and porous plate) were employed. The liquid flow starts developing from the sparger where non-uniformities in the gas sparging exist. From z/D ≥ 2 (z = axial location; D = column diameter), the fully developed axial liquid velocity profiles are seen. The radial variation of mean axial velocity shows gross liquid circulation in the column. Circulation velocities are smaller for the bubble column with porous plate sparger mainly due to the fact that the mean bubble size is small and the gas distribution is relatively uniform over the column cross-section. The difference in the hydrodynamic behavior with two different spargers is also apparent from the profiles of the turbulent kinetic energy and Reynolds stress measured from the velocity−time series.

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“…Therefore, the extent of liquid mixing is reduced at elevated pressures. Our recent study of flow fields and Reynolds stresses in high-pressure bubble Ž columns using the laser Doppler velocimetry technique Lee . et al, 2001 also confirmed that the bubble-induced turbulence of the liquid phase is depressed as the pressure increases.…”

Section: Effect Of System Pressurementioning

confidence: 99%