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Journal ArticleDOI

A new experimental technique to study backmixing in packed bubble columns

01 Oct 1992-Chemical Engineering Science (Pergamon)-Vol. 47, pp 4063-4067
TL;DR: In this paper, a new experimental technique was presented for the measurement of axial dispersion of a liquid in semibatch packed bubble columns, where the liquid used were water and mixtures of glycerine and water with viscosities up to 1.0 Pa s.
About: This article is published in Chemical Engineering Science.The article was published on 1992-10-01. It has received 7 citations till now. The article focuses on the topics: Dispersion (chemistry) & Bubble.
Citations
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Journal ArticleDOI
TL;DR: In this paper, an extensive study on the gas holdup, axial liquid dispersion, and mass transfer for packed, trayed, and empty bubble columns is presented. And the effect of the liquid and gas flow rates, liquid-phase viscosity, and type of internals is discussed in detail.
Abstract: This article presents an extensive study on the gas holdup, axial liquid dispersion, and mass transfer for packed, trayed, and empty bubble columns. Four types of structured packings (Super-Pak, Flexipac, Mellapak, and Gauze) and two types of perforated partition trays (with 25% and 40% tray open area) were used to characterize the packed and trayed bubble columns, respectively. It was observed that the gas holdup and mass transfer characteristics of the packed and trayed bubble columns are superior to those of an empty bubble column, while the axial dispersion coefficients are much lower. This article discusses in detail the effect of the liquid and gas flow rates, liquid-phase viscosity, and type of internals. Additionally, experimental data of the packed, trayed, and empty bubble column are correlated by dimensionless numbers. Novel empirical correlations are proposed for the gas holdup, Bodenstein number (for the axial dispersion coefficient), and Stanton number (for the volumetric mass transfer coefficient), as a function of the Froude and Galileo dimensionless numbers.

40 citations

Journal ArticleDOI
TL;DR: In this paper, the gas holdup and liquid axial dispersion coefficient are measured in two semibatch packed bubble columns, 0.154 and 0.200m diameter for an air-water system, at atmospheric conditions.

20 citations

Journal ArticleDOI
TL;DR: In this article, the authors investigated the gas holdup, frictional pressure drop and liquid dispersion in a packed bubble column at elevated pressures for the air-water system, which had an internal diameter of 0.15m and was packed with 15mm plastic rings.

16 citations

Journal ArticleDOI
TL;DR: In this article, a mixture of benzyl-alcohol and ethyl alcohol was index matched against the packing material to separate the signals from liquid and bubbles, and it was found that the axial time-averaged liquid velocity was lower than that obtained in empty bubble columns.

5 citations

Journal ArticleDOI
TL;DR: The effect of vertical baffles on the mixing process in a flotation column has been investigated in this paper, where it was found that the presence of vertical bifolds accelerated the liquid flow, leading to an almost complete mixing of the collection zone.

3 citations

References
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Journal ArticleDOI
TL;DR: In this article, the authors proposed a method to predict the distribution of residence-times in large systems by using distribution-functions for residencetimes, which can be used to calculate the etficiencies of reactors and blenders.

1,416 citations

Journal ArticleDOI
TL;DR: In this article, the authors measured the concentration profiles of oxygen in the liquid phase and obtained the kLa data of the various liquid phases which only depend on the gas velocity, adjusting the experimental profiles with the predictions of the axial dispersed plug flow model.

373 citations

Journal ArticleDOI
TL;DR: In this article, a review of the state of the art on backmixing in gas-liquid and gas-liquefied solid-reactor applications is presented, with a brief outline of various techniques for measuring residence time distribution (RTD) of various phases in a multiphase reactor is presented.
Abstract: 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.

131 citations

Journal ArticleDOI
TL;DR: In this article, the diffusion equations required are summarized in the present paper and their application is illustrated by typical experiments for diffusion into a solid from a gas or a liquid solution, the constant-volume method of measuring the diffusion coefficient has distinct experimental advantages.
Abstract: For diffusion into a solid from a gas or a liquid solution, the constant-volume method of measuring the diffusion coefficient has distinct experimental advantages. The diffusion equations required are summarized in the present paper and their application is illustrated by typical experiments. To reduce the amount of computation, equations involving error functions have been derived for application to the first stages of a diffusion run. When the diffusion coefficient and/or the sorption coefficient are concentration dependent, the equations in this paper are still applicable if sorption is carried out in suitably chosen steps. When sorption takes place only at the two parallel faces of a slab (film, sheet or plug), simple and rapid methods of calculating D can be used.

128 citations