Gas Holdup and Heat Transfer From Immersed Surfaces in Two- And Three-Phase Systems in Bubble Columns

Abstract

Two experimental slurry bubble column facilities comprising of 10.8 and 30.5 ern diameter columns and appropriate for conducting hydrodynamic and heat transfer studies arc described. The average and local gas holdup data are reported for the air-water system as a function of air velocity. The holdups for th" three phases are also reported for the air-water-glass beads system over a range of air velocity values.. The air holdup data are compared with the predictions of some of the commonly used correlations. The heat transfer coefficient for a 19 mm diameter cylindrical probe and the two-and three-phase dispersions are measured as a function of air velocity. Most of these hydrodynamic and heat transfer data correspond to the churn turbulent regime and the values obtained on the two columns differ appreciably from each other under similar operating conditions. This fact indicates that the scaleup of slurry bubble columns could be quite difficult on the basis of data obtained on the bench and pilot-plant scale units. The continuing data from these facilities on different systems will shed more light in the future on this important aspect which is crucial to the commercialization of indirect coal liquefaction technology.

Experiments and modeling of bubble column dehumidifier performance

“…Due to the excellent mixing in the bubble column, there is a negligible radial temperature gradient [23] and essentially zero resistance to radial mixing. Though temperature gradients have been observed in the vertical direction in industrial bubble columns [24], the depth of the liquid used in this experiment is only about 1-10% of the height of a typical bubble column.…”

Heat Transfer and Hydrodynamics in a Three-Phase Slurry Bubble Column

“…For bubble columns and slurry bubble columns, gas holdup has been found to increase with increasing superficial gas velocity (Kim et al, 1972;Koide et al, 1984;Fan et ai. 1987;Saxena et al, 1989Saxena et al, , 1990a. In the dispersed bubble 80w regime, this increase has been found to be proportional to surperfïcal gas velocity (Bach and Pilhofer, 1978;Lockett and Kirkpaûick, 1975;Kara et al, 1982 Wolff et al, 1990) reported that high superficial gas velocity, higher solids concentrations and particle densities resulted in larger bubbles and consequently lower gas holdup.…”

“…The influence of slurry concentration on heat transfer coefficient has been investigated by Kolbel et al (1958Kolbel et al ( , 1960, Deckwer et al (1980) and Saxena et al (1989Saxena et al ( , 1990a,…”

“…Heat transfer in slurry bubble colurnns has been investigated by several researchen (Deckwer et al, 1980; Saxena et al, 1989Saxena et al, , 1990, 1 992a). Generally a weak dependence of the heat transfer coefficient on the sluny concentration has k e n observed.…”

“…The measurements of heat transfer in particdate muftiphase systerns can be divided into object-to-bed (Deckwer et al, 1980;Saxena et al, 1989 and1990a) or wall-to-bed heat transfer (Chiu and Ziegler, 1983;Saberian-Broudjenni et al, 1985). In this study, the measurements of heat tram fer coefficients belong to object-to-bed heat tram fer.…”