Durchmischung in Blasensäulen

Badura, Reiner; Deckwer, Wolf‐Dieter; Warnecke, Hans‐Joachim; Langemann, Horst

doi:10.1002/cite.330460909

Cited by 34 publications

(5 citation statements)

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“…39,40 Liquid phase RTD measurements using stimulus-response techniques are a common tool to evaluate the hydrodynamics of gas-liquid fluidized beds and bubble column reactors. 20,41,42 Tracer material is usually injected into the system upstream as a pulse or a step input and monitored downstream. Following the work of Levenspiel and co-workers [43][44][45] the onedimensional axial dispersion model is used to analyze the RTD curves.…”

Section: Residence Time Distributionmentioning

confidence: 99%

Transport and reaction in microscale segmented gas–liquid flow

et al. 2004

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We use micro particle image velocimetry (microPIV) and fluorescence microscopy techniques to characterize microscale segmented gas-liquid flow at low superficial velocities relevant for chemical reactions with residence times of up to several minutes. Different gas-liquid microfluidic channel networks of rectangular cross section are fabricated in poly(dimethylsiloxane) (PDMS) using soft lithography techniques. The recirculation motion in the liquid segments associated with gas-liquid flows as well as the symmetry characteristics of the recirculations are quantified for straight and meandering channel networks. Even minor surface roughness effects and the compressibility of the gas phase induce loss of symmetry and enhance mixing across the centerline in straight channels. Mixing is further accelerated in meandering channels by the periodic switching of recirculation patterns across the channel center. We demonstrate a new, piezoelectrically activated flow injection technique for determining residence time distributions (RTDs) of fluid elements in multiphase microfluidic systems. The results confirm a narrowed liquid phase RTD in segmented flows in comparison to their single-phase counterparts. The enhanced mixing and narrow RTD characteristics of segmented gas-liquid flows are applied to liquid mixing and in sol-gel synthesis of colloidal nanoparticles.

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Section: Residence Time Distributionmentioning

confidence: 99%

Transport and reaction in microscale segmented gas–liquid flow

et al. 2004

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“…Some of these are summarized in Table 4. Early reviews on this subject are given by Mashelkar (1970), Eischoff ( 1966), Pavlica and Olson (1970), and Badura et al (1974). Figure 3 presents a schematic diagram of a vertically sparged bubble column.…”

Section: Gas-liquid Sparged Aeactors: Verticalmentioning

confidence: 99%

Backmixing in gas‐liquid reactors

1978

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This review evaluates the present state of the art on backmixing in gas-liquid and gas-liquid-solid reactors. A brief outline of numerous techniques for measuring residence time distribution (RTD) of various phases in a multiphase reactor is presented. This is followed by a brief description of differential and stagewise models for characterizing backmixing from RTD measurements. Both simple (that is, single-parameter axial dispersion model) and more complex (that is, two-, three-, or four-parameter models) models are evaluated. Backmixing characteristics of various gas-liquid columns such as trickle beds, spray columns, mechanically agitated columns, plate columns, fluidized bed columns, etc., are subsequently evaluated. The performance of a bubble column under various reaction conditions is analyzed. Criteria for the elimination of backmixing in packed-bed reactors are presented, and the effect of backmixing on the multiple steady states in a gas-liquid reactor is briefly reviewed. Finally, the scale-up problems associated with gas-liquid reactors with various degrees of backmixing and the recommendations for the future work in RTD and macromixing models are outlined. SCOPEIt is well known that backmixing is detrimental to the performance of a gas-liquid or a gas-liquid-solid reactor. This review outlines various aspects of backmixing in gas-liquid reactors.The review first outlines the methods for measuring residence time distributions for various phases in a gasliquid and a gas-liquid-solid reactor. The data for the residence time distributions (RTD) are evaluated by a variety of simple (for example, one-parameter axial dispersion model) and complex (for example, two-, three-, or four-parameter) differential or stagewise macromixing models. These models are briefly evaluated.From the point of view of backmixing, gay-liquid and gas-liquid-solid reactors can be classified into three broad categories: film reactors where the liquid is the dispersed phase and flows as a film, for example, trickle-bed reactors; gas dispersed as bubbles in a continuous liquid phase, for example, bubble column and slurry reactors; and liquid dispersed as droplets in a continuous gas phase, for example, spray column reactors. Backmixing characteristics of each of these types of reactors are briefly evaluated. The backmixing in these reactors has been largely characterized on the basis of axial dispersion model. Models for gas-liquid bubble column reactors are briefly reviewed. Slow, fast, and instantaneous gas-liquid reactions are considered. Criteria for eliminating the effect of backmixing on the performance of isothermal and adiabatic trickle-bed reactors are outlined. Unlike a singlephase reactor, an adiabatic gas-liquid reactor can lead to five steady states, and the literature on this unique feature of the gas-liquid reactor is briefly reviewed.Finally, there is a brief outline of the scale-up problems associated with RTD, and some recommendations for the future work on RTD and macromixing models are presented. CONCLUSIONS AND...

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“…Columns of 0.10 m are often applied for laboratory bubble column studies , , . On the other hand, it is commonly assumed that columns with diameters larger than 0.30 m are required to obtain results applicable for industrial scales , , .…”

Section: Methodsmentioning

confidence: 99%

Comparative Hydrodynamic Analysis of Narrow and Pilot‐Scale Bubble Columns with Internals

Möller

Kipping

Schleicher

et al. 2019

Chemie Ingenieur Technik

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For a stable operation of exothermic processes in bubble column reactors, an appropriate heat control is required, e.g., through dense internal tube bundle heat exchangers. Their impact on hydrodynamic characteristics and scaling approaches is studied for columns of different scales. Two different column dimensions (DN100 and DN400) were equipped with two common tube patterns of triangular and square pitches to study local fluid dynamics. Based on geometrical tube bundle scaling quantities, hydrodynamic similarity as a scale‐up criterion with respect to average holdups, phase distributions, and local gas structures can be reached.

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Durchmischung in Blasensäulen

Cited by 34 publications

References 0 publications

Transport and reaction in microscale segmented gas–liquid flow

Transport and reaction in microscale segmented gas–liquid flow

Backmixing in gas‐liquid reactors

Comparative Hydrodynamic Analysis of Narrow and Pilot‐Scale Bubble Columns with Internals

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